Calibration for a tunable rf filter structure

ABSTRACT

Embodiments of radio frequency (RF) front-end circuitry are disclosed where the RF front-end circuitry includes a tunable RF filter structure and a calibration circuit. The tunable RF filter structure includes (at least) a pair of weakly coupled resonators and defines a transfer function with a passband. The calibration circuit is configured to shape the passband so that the passband defines a center frequency. Additionally, the calibration circuit is configured to detect a phase difference at the target center frequency between the pair of weakly coupled resonators and adjust the phase difference of the pair of weakly coupled resonators at the target center frequency so as to reduce a frequency displacement between the center frequency of the passband and the target center frequency. In this manner, the calibration circuit calibrates the tunable RF filter structure to correct for errors in the center frequency of the passband due to component manufacturing variations.

RELATED APPLICATIONS

The present application claims priority to U.S. Provisional Patent Application No. 61/860,932, filed Aug. 1, 2013; U.S. Provisional Patent Application No. 61/909,028, filed Nov. 26, 2013; U.S. Provisional Patent Application No. 61/938,884, filed Feb. 12, 2014; U.S. Provisional Patent Application No. 61/949,581, filed Mar. 7, 2014; U.S. Provisional Patent Application No. 61/951,844, filed Mar. 12, 2014; U.S. Provisional Patent Application No. 61/982,946, filed Apr. 23, 2014; U.S. Provisional Patent Application No. 61/982,952, filed Apr. 23, 2014; U.S. Provisional Patent Application No. 61/982,971, filed Apr. 23, 2014; U.S. Provisional Patent Application No. 62/008,192, filed Jun. 5, 2014; and U.S. Provisional Patent Application No. 62/031,645, filed Jul. 31, 2014.

The present application claims the benefit of and is a Continuation-in-Part of U.S. patent application Ser. No. 14/298,829, filed Jun. 6, 2014, entitled “TUNABLE RF FILTER STRUCTURE FORMED BY A MATRIX OF WEAKLY COUPLED RESONATORS;” U.S. patent application Ser. No. 14/298,830, filed Jun. 6, 2014, entitled “TUNABLE RF FILTER PATHS FOR TUNABLE RF FILTER STRUCTURES;” U.S. patent application Ser. No. 14/298,834, filed Jun. 6, 2014, entitled “HIGH QUALITY FACTOR INTERCONNECT FOR RF CIRCUITS;” U.S. patent application Ser. No. 14/298,872, filed Jun. 6, 2014, entitled “NONLINEAR CAPACITANCE LINEARIZATION;” U.S. patent application Ser. No. 14/298,863, filed Jun. 6, 2014, entitled “TUNABLE RF FILTER BASED RF COMMUNICATIONS SYSTEM;” and U.S. patent application Ser. No. 14/298,852, filed Jun. 6, 2014, entitled “MULTI-BAND INTERFERENCE OPTIMIZATION.”

The present application is related to concurrently filed U.S. patent application Ser. No. ______, entitled “COOPERATIVE TUNABLE RF FILTERS;” concurrently filed U.S. patent application Ser. No. ______, entitled “ADVANCED 3D INDUCTOR STRUCTURES WITH CONFINED MAGNETIC FIELD;” concurrently filed U.S. patent application Ser. No. ______, entitled “VSWR DETECTOR FOR A TUNABLE RF FILTER STRUCTURE;” concurrently filed U.S. patent application Ser. No. ______, entitled “WEAKLY COUPLED TUNABLE RF RECEIVER ARCHITECTURE;” concurrently filed U.S. patent application Ser. No. ______, entitled “WEAKLY COUPLED TUNABLE RF TRANSMITTER ARCHITECTURE;” concurrently filed U.S. patent application Ser. No. ______, entitled “WEAKLY COUPLED TUNABLE RF TRANSMITTER ARCHITECTURE;” and concurrently filed U.S. patent application Ser. No. ______, entitled “BODY BIAS SWITCHING FOR AN RF SWITCH.”

All of the applications listed above are hereby incorporated herein by reference in their entireties.

FIELD OF THE DISCLOSURE

Embodiments of the present disclosure relate to radio frequency (RF) communications systems, which may include RF front-end circuitry, RF transceiver circuitry, RF amplifiers, direct current (DC)-DC converters, RF filters, RF antennas, RF switches, RF combiners, RF splitters, the like, or any combination thereof.

BACKGROUND

As wireless communications technologies evolve, wireless communications systems become increasingly sophisticated. As such, wireless communications protocols continue to expand and change to take advantage of the technological evolution. As a result, to maximize flexibility, many wireless communications devices must be capable of supporting any number of wireless communications protocols, each of which may have certain performance requirements, such as specific out-of-band emissions requirements, linearity requirements, or the like. Further, portable wireless communications devices are typically battery powered and need to be relatively small, and have low cost. As such, to minimize size, cost, and power consumption, RF circuitry in such a device needs to be as simple, small, flexible, and efficient as is practical. Thus, there is a need for RF circuitry in a communications device that is low cost, small, simple, flexible, and efficient.

SUMMARY

Embodiments of radio frequency (RF) front-end circuitry are disclosed along with exemplary methods of operating the same. In one embodiment, the RF front-end circuitry includes a tunable RF filter structure and a calibration circuit that calibrates the tunable RF filter structure. The tunable RF filter structure includes (at least) a pair of weakly coupled resonators and defines a transfer function with a passband. The calibration circuit is configured to shape the passband so that the passband defines a center frequency. Additionally, the calibration circuit is configured to detect a phase difference at the target center frequency between the pair of weakly coupled resonators and adjust the phase difference of the pair of weakly coupled resonators at the target center frequency so as to reduce a frequency displacement between the center frequency of the passband and the target center frequency. In this manner, the calibration circuit calibrates the tunable RF filter structure to correct for errors in the center frequency of the passband due to component manufacturing variations. Furthermore, by using the phase difference to reduce the frequency displacement between the center frequency of the passband and the target center frequency, the center frequency can be calibrated much more accurately. Finally, in some embodiments, the calibration circuit can also be used to place a notch adjacent to the passband approximately at a target notch frequency. This allows for greater out-of-band rejection and enhances the performance of the tunable RF filtering structure.

Those skilled in the art will appreciate the scope of the present disclosure and realize additional aspects thereof after reading the following detailed description of the preferred embodiments in association with the accompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings incorporated in and forming a part of this specification illustrate several aspects of the disclosure, and together with the description serve to explain the principles of the disclosure.

FIG. 1 shows traditional communications circuitry according to the prior art.

FIG. 2 shows the traditional communications circuitry according to the prior art.

FIG. 3 shows the traditional communications circuitry according to the prior art.

FIG. 4 shows RF communications circuitry according to one embodiment of the RF communications circuitry.

FIG. 5 is a graph illustrating filtering characteristics of a first tunable RF filter path and a second tunable RF filter path illustrated in FIG. 4 according to one embodiment of the first tunable RF filter path and the second tunable RF filter path.

FIGS. 6A and 6B are graphs illustrating filtering characteristics of the first tunable RF filter path and the second tunable RF filter path, respectively, illustrated in FIG. 4 according to an alternate embodiment of the first tunable RF filter path and the second tunable RF filter path, respectively.

FIG. 7 shows the RF communications circuitry according to one embodiment of the RF communications circuitry.

FIG. 8 shows the RF communications circuitry according to an alternate embodiment of the RF communications circuitry.

FIGS. 9A and 9B are graphs illustrating filtering characteristics of the first tunable RF filter path and the second tunable RF filter path, respectively, illustrated in FIG. 8 according to an additional embodiment of the first tunable RF filter path and the second tunable RF filter path.

FIGS. 10A and 10B are graphs illustrating filtering characteristics of a first traditional RF duplexer and a second traditional RF duplexer, respectively, illustrated in FIG. 3 according to the prior art.

FIG. 11 shows the RF communications circuitry according to one embodiment of the RF communications circuitry.

FIG. 12 shows the RF communications circuitry according to an alternate embodiment of the RF communications circuitry.

FIG. 13 shows the RF communications circuitry according to an additional embodiment of the RF communications circuitry.

FIG. 14 shows the RF communications circuitry according to another embodiment of the RF communications circuitry.

FIG. 15 shows the RF communications circuitry according to a further embodiment of the RF communications circuitry.

FIG. 16 shows the RF communications circuitry according to one embodiment of the RF communications circuitry.

FIG. 17 shows the RF communications circuitry according to an alternate embodiment of the RF communications circuitry.

FIG. 18 shows the RF communications circuitry according to an additional embodiment of the RF communications circuitry.

FIG. 19 shows the RF communications circuitry according to another embodiment of the RF communications circuitry.

FIG. 20 shows the RF communications circuitry according to a further embodiment of the RF communications circuitry.

FIG. 21 illustrates one embodiment of a tunable radio frequency (RF) filter structure that defines multiple tunable RF filtering paths that are independent of each other.

FIG. 22 illustrates one embodiment of a tunable RF filter path shown in FIG. 21 having cross-coupling capacitors arranged in a V-bridge structure.

FIG. 23 illustrates another embodiment of the tunable RF filter path shown in FIG. 21 having cross-coupling capacitors arranged in an X-bridge structure.

FIG. 24 illustrates another embodiment of the tunable RF filter path shown in FIG. 21 having a cross-coupling capacitor arranged in a single positive bridge structure.

FIG. 25 illustrates another embodiment of the tunable RF filter path shown in FIG. 21 having cross-coupling capacitors arranged in an H-bridge structure.

FIG. 26 illustrates another embodiment of the tunable RF filter path shown in FIG. 21 having cross-coupling capacitors arranged in a double H-bridge structure.

FIG. 27 illustrates another embodiment of the tunable RF filter path shown in FIG. 21 having four weakly coupled resonators with magnetic and electric couplings between them.

FIGS. 28A-28D disclose different embodiments of a tunable RF filter structure, each with a different number of input terminals and output terminals.

FIG. 29 illustrates one embodiment of a tunable radio frequency (RF) filter structure having four resonators and cross-coupling capacitive structures electrically connected between the four resonators so as to form a 2×2 matrix with the four resonators. In alternative embodiments, fewer (e.g., three) resonators or more (e.g., five or more) resonators may be provided.

FIG. 30 illustrates another embodiment of a tunable RF filter structure having M number of rows and N number of columns of resonators that are electrically connected by cross-coupling capacitive structures so that the tunable RF filter structure is arranged so as to form an M×N two-dimensional matrix of the resonators.

FIG. 31 illustrates the tunable RF filter structure shown in FIG. 30 electrically connected to various RF antennas.

FIG. 32 illustrates the tunable RF filter structure shown in FIG. 30 with two tunable RF filter paths highlighted for performing Multiple Input Multiple Output (MIMO), Single Input Multiple Output (SIMO), Multiple Input Single Output (MISO), and Single Input Single Output (SISO) operations.

FIG. 33 illustrates another embodiment of a tunable RF filter structure with amplifier stages electrically connected within and between tunable RF filter paths.

FIG. 34 illustrates an embodiment of a tunable RF filter structure integrated into an integrated circuit (IC) package with multiple and separate semiconductor dies.

FIG. 35 illustrates an embodiment of the same tunable RF filter structure shown in FIG. 34, but now integrated into an IC package with a single semiconductor die.

FIG. 36 illustrates one embodiment of a tunable RF filter structure having resonators and cross-coupling capacitive structures electrically connected between the resonators so as to form a three-dimensional matrix of the resonators.

FIG. 37 illustrates one embodiment of radio-frequency (RF) front-end circuitry that includes the first RF filter structure and a calibration circuit that calibrates the first RF filter structure.

FIG. 38 illustrates one embodiment of a transfer function of the first RF filter structure shown in FIG. 37 prior to calibration by the calibration circuit.

FIG. 39 illustrates one embodiment of the transfer function of the first RF filter structure shown in FIG. 37 after the calibration circuit has centered a passband of the transfer function approximately at a target center frequency.

FIG. 40 illustrates one embodiment of the transfer function of the first RF filter structure shown in FIG. 37 after the calibration circuit has placed a notch in the transfer function adjacent to the passband.

FIG. 41 illustrates an exemplary embodiment of the first RF filter structure shown in FIG. 37 having a matrix of resonators and an exemplary embodiment of the calibration circuit with a plurality of amplitude detectors and a plurality of phase detectors.

FIG. 42 illustrates an exemplary arrangement of weakly coupled resonators in the first RF filter structure with cross-coupling capacitors connected between the weakly coupled resonators and an exemplary arrangement phase detectors in the calibration circuit that allow the calibration circuit to adjust the variable capacitances of the cross-coupling capacitors in order to place a notch adjacent to the passband of the first RF filter structure.

FIG. 43 illustrates another exemplary arrangement of weakly coupled resonators in the first RF filter structure with a coupling capacitor connected between a terminal of the first RF filter structure and one the resonators along with an exemplary arrangement phase detectors in the calibration circuit that allow the calibration circuit to adjust the variable capacitance of the coupling capacitor to place a notch adjacent to the passband of the first RF filter structure.

FIG. 44 illustrates one embodiment of the calibration circuit, wherein in this embodiment, the calibration circuit includes a calibration computational device operably associated with the one or more phase detectors and a tuning control device operably associated with the first RF filter structure.

FIG. 45 illustrates one embodiment of a replica resonator, which may be provided in the calibration circuit to calibrate the first RF filter structure.

DETAILED DESCRIPTION

The embodiments set forth below represent the necessary information to enable those skilled in the art to practice the disclosure and illustrate the best mode of practicing the disclosure. Upon reading the following description in light of the accompanying drawings, those skilled in the art will understand the concepts of the disclosure and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure and the accompanying claims.

RF communications circuitry, which includes a first RF filter structure, is disclosed according to a first embodiment of the present disclosure. The first RF filter structure includes a first tunable RF filter path and a second tunable RF filter path. The first tunable RF filter path includes a pair of weakly coupled resonators. Additionally, a first filter parameter of the first tunable RF filter path is tuned based on a first filter control signal. A first filter parameter of the second tunable RF filter path is tuned based on a second filter control signal.

In one embodiment of the first RF filter structure, the first tunable RF filter path is directly coupled between a first common connection node and a first connection node. The second tunable RF filter path is directly coupled between a second connection node and the first common connection node.

In one embodiment of the RF communications system, the first tunable RF filter path and the second tunable RF filter path do not significantly load one another at frequencies of interest. As such, by directly coupling the first tunable RF filter path and the second tunable RF filter path to the first common connection node; front-end RF switching elements may be avoided, thereby reducing cost, size, and non-linearity; and increasing efficiency and flexibility of the RF communications system. In one embodiment of the RF communications system, the first common connection node is coupled to an antenna.

Embodiments of the RF communications system include frequency division duplex (FDD) applications, time division duplex (TDD) applications, carrier-aggregation (CA) applications, multiple antenna applications, MIMO applications, hybrid applications, applications supporting multiple communications bands, the like, or any combination thereof.

FIG. 1 shows traditional communications circuitry 10 according to the prior art. The traditional communications circuitry 10 illustrated in FIG. 1 is a time-division duplex (TDD) system, which is capable of transmitting and receiving RF signals, but not simultaneously. Such a system may also be called a half-duplex system. Additionally, the traditional communications circuitry 10 may be used as a simplex system, which is a system that only transmits RF signals or only receives RF signals. Traditional communications systems often use fixed frequency filters. As a result, to cover multiple communications bands, switching elements are needed to select between different signal paths.

The traditional communications circuitry 10 includes traditional RF system control circuitry 12, traditional RF front-end circuitry 14, and a first RF antenna 16. The traditional RF front-end circuitry 14 includes traditional RF front-end control circuitry 18, first traditional antenna matching circuitry 20, first traditional RF receive circuitry 22, first traditional RF transmit circuitry 24, a first traditional RF switch 26, and a second traditional RF switch 28. The first traditional RF switch 26 is coupled between the first traditional antenna matching circuitry 20 and the first traditional RF receive circuitry 22. The second traditional RF switch 28 is coupled between the first traditional antenna matching circuitry 20 and the first traditional RF transmit circuitry 24. The first RF antenna 16 is coupled to the first traditional antenna matching circuitry 20. The first traditional antenna matching circuitry 20 provides at least partial impedance matching between the first RF antenna 16 and either the first traditional RF receive circuitry 22 or the first traditional RF transmit circuitry 24.

The traditional RF system control circuitry 12 provides the necessary control functions needed to facilitate RF communications between the traditional communications circuitry 10 and other RF devices. The traditional RF system control circuitry 12 processes baseband signals needed for the RF communications. As such, the traditional RF system control circuitry 12 provides a first traditional upstream transmit signal TUT1 to the first traditional RF transmit circuitry 24. The first traditional upstream transmit signal TUT1 may be a baseband transmit signal, an intermediate frequency (IF) transmit signal, or an RF transmit signal. Conversely, the traditional RF system control circuitry 12 receives a first traditional downstream receive signal TDR1 from the first traditional RF receive circuitry 22. The first traditional downstream receive signal TDR1 may be a baseband receive signal, an IF receive signal, or an RF receive signal.

The first traditional RF transmit circuitry 24 may include up-conversion circuitry, amplification circuitry, power supply circuitry, filtering circuitry, switching circuitry, combining circuitry, splitting circuitry, dividing circuitry, clocking circuitry, the like, or any combination thereof. Similarly, the first traditional RF receive circuitry 22 may include down-conversion circuitry, amplification circuitry, power supply circuitry, filtering circuitry, switching circuitry, combining circuitry, splitting circuitry, dividing circuitry, clocking circuitry, the like, or any combination thereof.

The traditional RF system control circuitry 12 provides a traditional front-end control signal TFEC to the traditional RF front-end control circuitry 18. The traditional RF front-end control circuitry 18 provides a first traditional switch control signal TCS1 and a second traditional switch control signal TCS2 to the first traditional RF switch 26 and the second traditional RF switch 28, respectively, based on the traditional front-end control signal TFEC. As such, the traditional RF system control circuitry 12 controls the first traditional RF switch 26 and the second traditional RF switch 28 via the traditional front-end control signal TFEC. The first traditional RF switch 26 is in one of an ON state and an OFF state based on the first traditional switch control signal TCS1. The second traditional RF switch 28 is in one of an ON state and an OFF state based on the second traditional switch control signal TCS2.

Half-duplex operation of the traditional communications circuitry 10 is accomplished using the first traditional RF switch 26 and the second traditional RF switch 28. When the traditional communications circuitry 10 is transmitting RF signals via the first RF antenna 16, the first traditional RF switch 26 is in the OFF state and the second traditional RF switch 28 is in the ON state. As such, the first traditional antenna matching circuitry 20 is electrically isolated from the first traditional RF receive circuitry 22 and the first traditional antenna matching circuitry 20 is electrically coupled to the first traditional RF transmit circuitry 24. In this regard, the traditional RF system control circuitry 12 provides the first traditional upstream transmit signal TUT1 to the first traditional RF transmit circuitry 24, which provides a traditional transmit signal TTX to the first RF antenna 16 via the second traditional RF switch 28 and the first traditional antenna matching circuitry 20 based on the first traditional upstream transmit signal TUT1.

When the traditional communications circuitry 10 is receiving RF signals via the first RF antenna 16, the first traditional RF switch 26 is in the ON state and the second traditional RF switch 28 is in the OFF state. As such, the first traditional antenna matching circuitry 20 is isolated from the first traditional RF transmit circuitry 24 and the first traditional antenna matching circuitry 20 is electrically coupled to the first traditional RF receive circuitry 22. In this regard, the first traditional antenna matching circuitry 20 receives the RF signals from the first RF antenna 16 and forwards the RF signals via the first traditional RF switch 26 to the first traditional RF receive circuitry 22. The first traditional RF switch 26 provides a traditional receive signal TRX to the first traditional RF receive circuitry 22, which provides a first traditional downstream receive signal TDR1 to the traditional RF system control circuitry 12 based on the traditional receive signal TRX.

Since the traditional communications circuitry 10 illustrated in FIG. 1 is a half-duplex system, during operation, the first traditional RF switch 26 and the second traditional RF switch 28 are not simultaneously in the ON state. Therefore, the first traditional RF receive circuitry 22 and the first traditional RF transmit circuitry 24 are isolated from one another. As such, the first traditional RF receive circuitry 22 and the first traditional RF transmit circuitry 24 are prevented from interfering with one another.

FIG. 2 shows the traditional communications circuitry 10 according to the prior art. The traditional communications circuitry 10 illustrated in FIG. 2 is similar to the traditional communications circuitry 10 illustrated in FIG. 1, except in the traditional communications circuitry 10 illustrated in FIG. 2, the traditional RF front-end control circuitry 18, the first traditional RF switch 26, and the second traditional RF switch 28 are omitted, and the traditional RF front-end circuitry 14 further includes a first traditional RF duplexer 30. The first traditional RF duplexer 30 is coupled between the first traditional antenna matching circuitry 20 and the first traditional RF receive circuitry 22, and is further coupled between the first traditional antenna matching circuitry 20 and the first traditional RF transmit circuitry 24.

The traditional communications circuitry 10 illustrated in FIG. 2 may be used as a TDD system or a simplex system. However, the traditional communications circuitry 10 illustrated in FIG. 2 may also be used as a frequency-division duplex (FDD) system, which is capable of transmitting and receiving RF signals simultaneously. Such a system may also be called a full-duplex system.

When the traditional communications circuitry 10 is transmitting RF signals via the first RF antenna 16, the traditional RF system control circuitry 12 provides the first traditional upstream transmit signal TUT1 to the first traditional RF transmit circuitry 24, which provides the traditional transmit signal TTX to the first RF antenna 16 via first traditional RF duplexer 30 based on the first traditional upstream transmit signal TUT1.

When the traditional communications circuitry 10 is receiving RF signals via the first RF antenna 16, the first traditional antenna matching circuitry 20 receives the RF signals from the first RF antenna 16 and forwards the RF signals via the first traditional RF duplexer 30 to the first traditional RF receive circuitry 22. As such, the first traditional RF duplexer 30 provides the traditional receive signal TRX to the first traditional RF receive circuitry 22, which provides the first traditional downstream receive signal TDR1 to the traditional RF system control circuitry 12 based on the traditional receive signal TRX.

The first traditional RF duplexer 30 provides filtering, such that the first traditional RF receive circuitry 22 and the first traditional RF transmit circuitry 24 are substantially isolated from one another. As such, the first traditional RF receive circuitry 22 and the first traditional RF transmit circuitry 24 are prevented from interfering with one another. Traditional FDD systems using duplexers with high rejection ratios have a fixed frequency transfer. Covering multiple communications bands requires multiple duplexers and switches to route RF signals through appropriate signal paths.

FIG. 3 shows the traditional communications circuitry 10 according to the prior art. The traditional communications circuitry 10 illustrated in FIG. 3 is a carrier aggregation (CA) based system, which is capable of transmitting or receiving multiple simultaneous transmit signals or multiple simultaneous receive signals, respectively, or both. Each of the simultaneous transmit signals is in a frequency band that is different from each frequency band of a balance of the simultaneous transmit signals. Similarly, each of the simultaneous receive signals is in a frequency band that is different from each frequency band of a balance of the simultaneous receive signals. The traditional communications circuitry 10 may operate as a simplex system, a half-duplex system, or a full-duplex system.

The traditional communications circuitry 10 includes the traditional RF system control circuitry 12, the traditional RF front-end circuitry 14, the first RF antenna 16, and a second RF antenna 32. The traditional RF front-end circuitry 14 includes the first traditional antenna matching circuitry 20, the first traditional RF receive circuitry 22, the first traditional RF transmit circuitry 24, the first traditional RF duplexer 30, first traditional antenna switching circuitry 34, a second traditional RF duplexer 36, a third traditional RF duplexer 38, second traditional antenna matching circuitry 40, second traditional antenna switching circuitry 42, a fourth traditional RF duplexer 44, a fifth traditional RF duplexer 46, a sixth traditional RF duplexer 48, second traditional RF receive circuitry 50, and second traditional RF transmit circuitry 52. Traditional CA systems use fixed frequency filters and diplexers, triplexers, or both to combine signal paths, which increases complexity. Alternatively, additional switch paths may be used, but may degrade performance.

The first traditional antenna matching circuitry 20 is coupled between the first RF antenna 16 and the first traditional antenna switching circuitry 34. The second traditional antenna matching circuitry 40 is coupled between the second RF antenna 32 and the second traditional antenna switching circuitry 42. The first traditional RF duplexer 30 is coupled between the first traditional antenna switching circuitry 34 and the first traditional RF receive circuitry 22, and is further coupled between the first traditional antenna switching circuitry 34 and the first traditional RF transmit circuitry 24. The second traditional RF duplexer 36 is coupled between the first traditional antenna switching circuitry 34 and the first traditional RF receive circuitry 22, and is further coupled between the first traditional antenna switching circuitry 34 and the first traditional RF transmit circuitry 24. The third traditional RF duplexer 38 is coupled between the first traditional antenna switching circuitry 34 and the first traditional RF receive circuitry 22, and is further coupled between the first traditional antenna switching circuitry 34 and the first traditional RF transmit circuitry 24.

The fourth traditional RF duplexer 44 is coupled between the second traditional antenna switching circuitry 42 and the second traditional RF receive circuitry 50, and is further coupled between the second traditional antenna switching circuitry 42 and the second traditional RF transmit circuitry 52. The fifth traditional RF duplexer 46 is coupled between the second traditional antenna switching circuitry 42 and the second traditional RF receive circuitry 50, and is further coupled between the second traditional antenna switching circuitry 42 and the second traditional RF transmit circuitry 52. The sixth traditional RF duplexer 48 is coupled between the second traditional antenna switching circuitry 42 and the second traditional RF receive circuitry 50, and is further coupled between the second traditional antenna switching circuitry 42 and the second traditional RF transmit circuitry 52.

The first traditional RF duplexer 30 is associated with a first aggregated receive band, a first aggregated transmit band, or both. The second traditional RF duplexer 36 is associated with a second aggregated receive band, a second aggregated transmit band, or both. The third traditional RF duplexer 38 is associated with a third aggregated receive band, a third aggregated transmit band, or both. The fourth traditional RF duplexer 44 is associated with a fourth aggregated receive band, a fourth aggregated transmit band, or both. The fifth traditional RF duplexer 46 is associated with a fifth aggregated receive band, a fifth aggregated transmit band, or both. The sixth traditional RF duplexer 48 is associated with a sixth aggregated receive band, a sixth aggregated transmit band, or both.

The first traditional antenna switching circuitry 34 couples a selected one of the first traditional RF duplexer 30, the second traditional RF duplexer 36, and the third traditional RF duplexer 38 to the first traditional antenna matching circuitry 20. Therefore, the first RF antenna 16 is associated with a selected one of the first aggregated receive band, the second aggregated receive band, and the third aggregated receive band; with a selected one of the first aggregated transmit band, the second aggregated transmit band, and the third aggregated transmit band; or both.

Similarly, the second traditional antenna switching circuitry 42 couples a selected one of the fourth traditional RF duplexer 44, the fifth traditional RF duplexer 46, and the sixth traditional RF duplexer 48 to the second traditional antenna matching circuitry 40. Therefore, the second RF antenna 32 is associated with a selected one of the fourth aggregated receive band, the fifth aggregated receive band, and the sixth aggregated receive band; with a selected one of the fourth aggregated transmit band, the fifth aggregated transmit band, and the sixth aggregated transmit band; or both.

During transmit CA, the traditional RF system control circuitry 12 provides the first traditional upstream transmit signal TUT1 to the first traditional RF transmit circuitry 24, which forwards the first traditional upstream transmit signal TUT1 to the first RF antenna 16 for transmission via the selected one of the first traditional RF duplexer 30, the second traditional RF duplexer 36, and the third traditional RF duplexer 38; via the first traditional antenna switching circuitry 34; and via the first traditional antenna matching circuitry 20.

Additionally, during transmit CA, the traditional RF system control circuitry 12 provides a second traditional upstream transmit signal TUT2 to the second traditional RF transmit circuitry 52, which forwards the second traditional upstream transmit signal TUT2 to the second RF antenna 32 for transmission via the selected one of the fourth traditional RF duplexer 44, the fifth traditional RF duplexer 46, and the sixth traditional RF duplexer 48; via the second traditional antenna switching circuitry 42; and via the second traditional antenna matching circuitry 40.

During receive CA, the first RF antenna 16 forwards a received RF signal to the first traditional RF receive circuitry 22 via the first traditional antenna matching circuitry 20, the first traditional antenna switching circuitry 34, and the selected one of the first traditional RF duplexer 30, the second traditional RF duplexer 36, and the third traditional RF duplexer 38. The first traditional RF receive circuitry 22 provides the first traditional downstream receive signal TDR1 to the traditional RF system control circuitry 12 based on the received RF signal.

Additionally, during receive CA, the second RF antenna 32 forwards a received RF signal to the second traditional RF receive circuitry 50 via the second traditional antenna matching circuitry 40, the second traditional antenna switching circuitry 42, and the selected one of the fourth traditional RF duplexer 44, the fifth traditional RF duplexer 46, and the sixth traditional RF duplexer 48. The second traditional RF receive circuitry 50 provides a second traditional downstream receive signal TDR2 to the traditional RF system control circuitry 12 based on the received RF signal.

Since only the selected one of the first traditional RF duplexer 30, the second traditional RF duplexer 36, and the third traditional RF duplexer 38 is coupled to the first traditional antenna matching circuitry 20; the first traditional antenna switching circuitry 34 isolates each of the first traditional RF duplexer 30, the second traditional RF duplexer 36, and the third traditional RF duplexer 38 from one another; and prevents each of the first traditional RF duplexer 30, the second traditional RF duplexer 36, and the third traditional RF duplexer 38 from interfering with one another.

Similarly, since only the selected one of the fourth traditional RF duplexer 44, the fifth traditional RF duplexer 46, and the sixth traditional RF duplexer 48 is coupled to the second traditional antenna matching circuitry 40; the second traditional antenna matching circuitry 40 isolates each of the fourth traditional RF duplexer 44, the fifth traditional RF duplexer 46, and the sixth traditional RF duplexer 48 from one another; and prevents each of the fourth traditional RF duplexer 44, the fifth traditional RF duplexer 46, and the sixth traditional RF duplexer 48 from interfering with one another.

FIG. 4 shows RF communications circuitry 54 according to one embodiment of the RF communications circuitry 54. The RF communications circuitry 54 includes RF system control circuitry 56, RF front-end circuitry 58, and the first RF antenna 16. The RF front-end circuitry 58 includes a first RF filter structure 60, RF receive circuitry 62, and RF transmit circuitry 64. The first RF filter structure 60 includes a first tunable RF filter path 66 and a second tunable RF filter path 68. Additionally, the first RF filter structure 60 has a first connection node 70, a second connection node 72, and a first common connection node 74. In one embodiment of the RF system control circuitry 56, the RF system control circuitry 56 is an RF transceiver. In one embodiment of the first tunable RF filter path 66, the first tunable RF filter path 66 includes a pair of weakly coupled resonators R(1,1), R(1,2) (FIG. 22). As such, in one embodiment of the first RF filter structure 60, the RF filter structure 60 includes the pair of weakly coupled resonators R(1,1), R(1,2) (FIG. 21).

In alternate embodiments of the first RF filter structure 60, any or all of the first connection node 70, the second connection node 72, and the first common connection node 74 are external to the first RF filter structure 60. In one embodiment of the first tunable RF filter path 66, the first tunable RF filter path 66 includes a first pair (not shown) of weakly coupled resonators. In one embodiment of the second tunable RF filter path 68, the second tunable RF filter path 68 includes a second pair (not shown) of weakly coupled resonators.

In one embodiment of the first RF filter structure 60, the first tunable RF filter path 66 is directly coupled between the first common connection node 74 and the first connection node 70, the second tunable RF filter path 68 is directly coupled between the second connection node 72 and the first common connection node 74, and the first RF antenna 16 is directly coupled to the first common connection node 74. In another embodiment of the RF communications circuitry 54, the first RF antenna 16 is omitted. Additionally, the RF receive circuitry 62 is coupled between the first connection node 70 and the RF system control circuitry 56, and the RF transmit circuitry 64 is coupled between the second connection node 72 and the RF system control circuitry 56.

In one embodiment of the RF communications circuitry 54, the first tunable RF filter path 66 is a first RF receive filter, such that the first RF antenna 16 forwards a received RF signal via the first common connection node 74 to provide a first upstream RF receive signal RU1 to the first tunable RF filter path 66, which receives and filters the first upstream RF receive signal RU1 to provide a first filtered RF receive signal RF1 to the RF receive circuitry 62. The RF receive circuitry 62 may include down-conversion circuitry, amplification circuitry, power supply circuitry, filtering circuitry, switching circuitry, combining circuitry, splitting circuitry, dividing circuitry, clocking circuitry, the like, or any combination thereof. The RF receive circuitry 62 processes the first filtered RF receive signal RF1 to provide a first receive signal RX1 to the RF system control circuitry 56.

In one embodiment of the RF communications circuitry 54, the second tunable RF filter path 68 is a first RF transmit filter, such that the RF system control circuitry 56 provides a first transmit signal TX1 to the RF transmit circuitry 64, which processes the first transmit signal TX1 to provide a first upstream RF transmit signal TU1 to the second tunable RF filter path 68. The RF transmit circuitry 64 may include up-conversion circuitry, amplification circuitry, power supply circuitry, filtering circuitry, switching circuitry, combining circuitry, splitting circuitry, dividing circuitry, clocking circuitry, the like, or any combination thereof. The second tunable RF filter path 68 receives and filters the first upstream RF transmit signal TU1 to provide a first filtered RF transmit signal TF1, which is transmitted via the first common connection node 74 by the first RF antenna 16.

The RF system control circuitry 56 provides a first filter control signal FCS1 to the first tunable RF filter path 66 and provides a second filter control signal FCS2 to the second tunable RF filter path 68. As such, in one embodiment of the RF communications circuitry 54, the RF system control circuitry 56 tunes a first filter parameter of the first tunable RF filter path 66 using the first filter control signal FCS1. Additionally, the RF system control circuitry 56 tunes a first filter parameter of the second tunable RF filter path 68 using the second filter control signal FCS2.

In one embodiment of the RF communications circuitry 54, the first tunable RF filter path 66 and the second tunable RF filter path 68 do not significantly load one another at frequencies of interest. As such, by directly coupling the first tunable RF filter path 66 and the second tunable RF filter path 68 to the first common connection node 74; front-end RF switching elements may be avoided, thereby reducing cost, size, and non-linearity; and increasing efficiency and flexibility of the RF communications circuitry 54. Since tunable RF filters can support multiple communications bands using a single signal path, they can simplify front-end architectures by eliminating switching and duplexing components.

In one embodiment of the RF communications circuitry 54, the RF communications circuitry 54 is used as an FDD communications system, such that the first upstream RF receive signal RU1 and the first filtered RF transmit signal TF1 are full-duplex signals. In an alternate embodiments of the RF communications circuitry 54, the RF communications circuitry 54 is used as a TDD communications system, such that the first upstream RF receive signal RU1 and the first filtered RF transmit signal TF1 are half-duplex signals. In additional embodiments of the RF communications circuitry 54, the RF communications circuitry 54 is used as a simplex communications system, such that the first upstream RF receive signal RU1 is a simplex signal and the first filtered RF transmit signal TF1 is not present. In other embodiments of the RF communications circuitry 54, the RF communications circuitry 54 is used as a simplex communications system, such that the first upstream RF receive signal RU1 is not present and the first filtered RF transmit signal TF1 is a simplex signal.

FIG. 5 is a graph illustrating filtering characteristics of the first tunable RF filter path 66 and the second tunable RF filter path 68 illustrated in FIG. 4 according to one embodiment of the first tunable RF filter path 66 and the second tunable RF filter path 68. The first tunable RF filter path 66 is a first RF bandpass filter, which functions as the first RF receive filter, and the second tunable RF filter path 68 is a second RF bandpass filter, which functions as the first RF transmit filter. A bandwidth 76 of the first RF bandpass filter, a center frequency 78 of the first RF bandpass filter, a bandwidth 80 of the second RF bandpass filter, a center frequency 82 of the second RF bandpass filter, a frequency 84 of the first upstream RF receive signal RU1 (FIG. 4), and a frequency 86 of the first filtered RF transmit signal TF1 (FIG. 4) are shown. Operation of the first RF bandpass filter and the second RF bandpass filter is such that the first RF bandpass filter and the second RF bandpass filter do not significantly interfere with one another. In this regard, the bandwidth 76 of the first RF bandpass filter does not overlap the bandwidth 80 of the second RF bandpass filter.

In one embodiment of the first RF receive filter and the first RF transmit filter, the first RF receive filter and the first RF transmit filter in combination function as an RF duplexer. As such, a duplex frequency 88 of the RF duplexer is about equal to a difference between the frequency 84 of the first upstream RF receive signal RU1 (FIG. 4) and the frequency 86 of the first filtered RF transmit signal TF1 (FIG. 4).

In one embodiment of the first tunable RF filter path 66, the first filter parameter of the first tunable RF filter path 66 is tunable based on the first filter control signal FCS1. In an alternate embodiment of the first tunable RF filter path 66, both the first filter parameter of the first tunable RF filter path 66 and a second filter parameter of the first tunable RF filter path 66 are tunable based on the first filter control signal FCS1. Similarly, in one embodiment of the second tunable RF filter path 68, the first filter parameter of the second tunable RF filter path 68 is tunable based on the second filter control signal FCS2. In an alternate embodiment of the second tunable RF filter path 68, both the first filter parameter of the second tunable RF filter path 68 and a second filter parameter of the second tunable RF filter path 68 are tunable based on the second filter control signal FCS2.

The first filter parameter of the first tunable RF filter path 66 is the center frequency 78 of the first RF bandpass filter. The second filter parameter of the first tunable RF filter path 66 is the bandwidth 76 of the first RF bandpass filter. The first filter parameter of the second tunable RF filter path 68 is the center frequency 82 of the second RF bandpass filter. The second filter parameter of the second tunable RF filter path 68 is the bandwidth 80 of the second RF bandpass filter.

FIGS. 6A and 6B are graphs illustrating filtering characteristics of the first tunable RF filter path 66 and the second tunable RF filter path 68, respectively, illustrated in FIG. 4 according to an alternate embodiment of the first tunable RF filter path 66 and the second tunable RF filter path 68, respectively. The first tunable RF filter path 66 is an RF lowpass filter and the second tunable RF filter path 68 is an RF highpass filter. FIG. 6A shows a frequency response curve 90 of the RF lowpass filter and FIG. 6B shows a frequency response curve 92 of the RF highpass filter. Additionally FIG. 6A shows a break frequency 94 of the RF lowpass filter and FIG. 6B shows a break frequency 96 of the RF highpass filter. Both FIGS. 6A and 6B show the frequency 84 of the first upstream RF receive signal RU1 (FIG. 4), the frequency 86 of the first filtered RF transmit signal TF1 (FIG. 4), and the duplex frequency 88 of the RF duplexer for clarification. However, the RF lowpass filter and the RF highpass filter in combination function as an RF diplexer. The first filter parameter of the first tunable RF filter path 66 is the break frequency 94 of the RF lowpass filter. In one embodiment of the RF lowpass filter, the RF lowpass filter has bandpass filter characteristics. The first filter parameter of the second tunable RF filter path 68 is the break frequency 96 of the RF highpass filter. In one embodiment of the RF highpass filter, the RF highpass filter has bandpass filter characteristics. In one embodiment of the RF diplexer, the break frequency 96 of the RF highpass filter is about equal to the break frequency 94 of the RF lowpass filter.

FIG. 7 shows the RF communications circuitry 54 according to one embodiment of the RF communications circuitry 54. The RF communications circuitry 54 illustrated in FIG. 7 is similar to the RF communications circuitry 54 illustrated in FIG. 4, except in the RF front-end circuitry 58 illustrated in FIG. 7, the RF transmit circuitry 64 (FIG. 4) is omitted and the RF front-end circuitry 58 further includes RF front-end control circuitry 98.

The RF system control circuitry 56 provides a front-end control signal FEC to the RF front-end control circuitry 98. The RF front-end control circuitry 98 provides the first filter control signal FCS1 and the second filter control signal FCS2 based on the front-end control signal FEC. In the RF communications circuitry 54 illustrated in FIG. 4, the RF system control circuitry 56 provides the first filter control signal FCS1 and the second filter control signal FCS2 directly. In general, the RF communications circuitry 54 includes control circuitry, which may be either the RF system control circuitry 56 or the RF front-end control circuitry 98, that provides the first filter control signal FCS1 and the second filter control signal FCS2. As such, in one embodiment of the RF communications circuitry 54, the control circuitry tunes a first filter parameter of the first tunable RF filter path 66 using the first filter control signal FCS1. Additionally, the control circuitry tunes a first filter parameter of the second tunable RF filter path 68 using the second filter control signal FCS2. In an additional embodiment of the RF communications circuitry 54, the control circuitry further tunes a second filter parameter of the first tunable RF filter path 66 using the first filter control signal FCS1; and the control circuitry further tunes a second filter parameter of the second tunable RF filter path 68 using the second filter control signal FCS2.

In alternate embodiments of the first RF filter structure 60, any or all of the first connection node 70, the second connection node 72, and the first common connection node 74 are external to the first RF filter structure 60. In one embodiment of the first tunable RF filter path 66, the first tunable RF filter path 66 includes a first pair (not shown) of weakly coupled resonators. In one embodiment of the second tunable RF filter path 68, the second tunable RF filter path 68 includes a second pair (not shown) of weakly coupled resonators.

In one embodiment of the first RF filter structure 60, the first tunable RF filter path 66 is directly coupled between the first common connection node 74 and the first connection node 70, the second tunable RF filter path 68 is directly coupled between the second connection node 72 and the first common connection node 74, and the first RF antenna 16 is directly coupled to the first common connection node 74. In another embodiment of the RF communications circuitry 54, the first RF antenna 16 is omitted. Additionally, the RF receive circuitry 62 is coupled between the first connection node 70 and the RF system control circuitry 56, and the RF receive circuitry 62 is further coupled between the second connection node 72 and the RF system control circuitry 56.

In one embodiment of the RF communications circuitry 54, the first tunable RF filter path 66 is a first RF receive filter, such that the first RF antenna 16 forwards a first received RF signal via the first common connection node 74 to provide a first upstream RF receive signal RU1 to the first tunable RF filter path 66, which receives and filters the first upstream RF receive signal RU1 to provide a first filtered RF receive signal RF1 to the RF receive circuitry 62. Additionally, the second tunable RF filter path 68 is a second RF receive filter, such that the first RF antenna 16 forwards a second received RF signal via the first common connection node 74 to provide a second upstream RF receive signal RU2 to the second tunable RF filter path 68, which receives and filters the second upstream RF receive signal RU2 to provide a second filtered RF receive signal RF2 to the RF receive circuitry 62.

The RF receive circuitry 62 may include down-conversion circuitry, amplification circuitry, power supply circuitry, filtering circuitry, switching circuitry, combining circuitry, splitting circuitry, dividing circuitry, clocking circuitry, the like, or any combination thereof. The RF receive circuitry 62 processes the first filtered RF receive signal RF1 to provide a first receive signal RX1 to the RF system control circuitry 56. Additionally, the RF receive circuitry 62 processes the second filtered RF receive signal RF2 to provide a second receive signal RX2 to the RF system control circuitry 56.

In one embodiment of the RF communications circuitry 54, the first tunable RF filter path 66 and the second tunable RF filter path 68 do not significantly load one another at frequencies of interest. As such, by directly coupling the first tunable RF filter path 66 and the second tunable RF filter path 68 to the first common connection node 74; front-end RF switching elements may be avoided, thereby reducing cost, size, and non-linearity; and increasing efficiency and flexibility of the RF communications circuitry 54.

In this regard, in one embodiment of the first tunable RF filter path 66 and the second tunable RF filter path 68, each of the first tunable RF filter path 66 and the second tunable RF filter path 68 is a bandpass filter having a unique center frequency. As such, the first filter parameter of each of the first tunable RF filter path 66 and the second tunable RF filter path 68 is a unique center frequency.

In an alternate embodiment of the first tunable RF filter path 66 and the second tunable RF filter path 68, one of the first tunable RF filter path 66 and the second tunable RF filter path 68 is a lowpass filter, and another of the first tunable RF filter path 66 and the second tunable RF filter path 68 is a highpass filter. As such, the first filter parameter of each of the first tunable RF filter path 66 and the second tunable RF filter path 68 is a break frequency.

In an additional embodiment of the first tunable RF filter path 66 and the second tunable RF filter path 68, one of the first tunable RF filter path 66 and the second tunable RF filter path 68 is a lowpass filter, and another of the first tunable RF filter path 66 and the second tunable RF filter path 68 is a bandpass filter. As such, the first filter parameter of one of the first tunable RF filter path 66 and the second tunable RF filter path 68 is a center frequency, and the first filter parameter of another of the first tunable RF filter path 66 and the second tunable RF filter path 68 is a break frequency.

In an additional embodiment of the first tunable RF filter path 66 and the second tunable RF filter path 68, one of the first tunable RF filter path 66 and the second tunable RF filter path 68 is a highpass filter, and another of the first tunable RF filter path 66 and the second tunable RF filter path 68 is a bandpass filter. As such, the first filter parameter of one of the first tunable RF filter path 66 and the second tunable RF filter path 68 is a center frequency, and the first filter parameter of another of the first tunable RF filter path 66 and the second tunable RF filter path 68 is a break frequency.

In one embodiment of the RF communications circuitry 54, the RF communications circuitry 54 is a receive only CA system, such that the first tunable RF filter path 66, which is the first RF receive filter, and the second tunable RF filter path 68, which is the second RF receive filter, simultaneously receive and filter the first upstream RF receive signal RU1 and the second upstream RF receive signal RU2, respectively, via the first common connection node 74. As such, the first RF filter structure 60 functions as a de-multiplexer. In this regard, each of the first upstream RF receive signal RU1 and the second upstream RF receive signal RU2 has a unique carrier frequency. Using receive CA may increase an effective receive bandwidth of the RF communications circuitry 54.

In another embodiment of the RF communications circuitry 54, the RF communications circuitry 54 is a receive only communications system, such that the first tunable RF filter path 66, which is the first RF receive filter, and the second tunable RF filter path 68, which is the second RF receive filter, do not simultaneously receive and filter the first upstream RF receive signal RU1 and the second upstream RF receive signal RU2, respectively. As such, the first upstream RF receive signal RU1 and the second upstream RF receive signal RU2 are nonsimultaneous signals. Each of the first upstream RF receive signal RU1 and the second upstream RF receive signal RU2 may be associated with a unique RF communications band.

FIG. 8 shows the RF communications circuitry 54 according to an alternate embodiment of the RF communications circuitry 54. The RF communications circuitry 54 illustrated in FIG. 8 is similar to the RF communications circuitry 54 illustrated in FIG. 7, except in the RF front-end circuitry 58 illustrated in FIG. 8, the RF receive circuitry 62 is omitted and the RF transmit circuitry 64 is included.

The RF system control circuitry 56 provides the front-end control signal FEC to the RF front-end control circuitry 98. The RF front-end control circuitry 98 provides the first filter control signal FCS1 and the second filter control signal FCS2 based on the front-end control signal FEC. In the RF communications circuitry 54 illustrated in FIG. 4, the RF system control circuitry 56 provides the first filter control signal FCS1 and the second filter control signal FCS2 directly. In general, the RF communications circuitry 54 includes control circuitry, which may be either the RF system control circuitry 56 or the RF front-end control circuitry 98, that provides the first filter control signal FCS1 and the second filter control signal FCS2. As such, in one embodiment of the RF communications circuitry 54, the control circuitry tunes a first filter parameter of the first tunable RF filter path 66 using the first filter control signal FCS1. Additionally, the control circuitry tunes a first filter parameter of the second tunable RF filter path 68 using the second filter control signal FCS2. In an additional embodiment of the RF communications circuitry 54, the control circuitry further tunes a second filter parameter of the first tunable RF filter path 66 using the first filter control signal FCS1; and the control circuitry further tunes a second filter parameter of the second tunable RF filter path 68 using the second filter control signal FCS2.

In alternate embodiments of the first RF filter structure 60, any or all of the first connection node 70, the second connection node 72, and the first common connection node 74 are external to the first RF filter structure 60. In one embodiment of the first tunable RF filter path 66, the first tunable RF filter path 66 includes a first pair (not shown) of weakly coupled resonators. In one embodiment of the second tunable RF filter path 68, the second tunable RF filter path 68 includes a second pair (not shown) of weakly coupled resonators.

In one embodiment of the first RF filter structure 60, the first tunable RF filter path 66 is directly coupled between the first common connection node 74 and the first connection node 70, the second tunable RF filter path 68 is directly coupled between the second connection node 72 and the first common connection node 74, and the first RF antenna 16 is directly coupled to the first common connection node 74. In another embodiment of the RF communications circuitry 54, the first RF antenna 16 is omitted. Additionally, the RF transmit circuitry 64 is coupled between the first connection node 70 and the RF system control circuitry 56, and the RF transmit circuitry 64 is further coupled between the second connection node 72 and the RF system control circuitry 56.

In one embodiment of the RF communications circuitry 54, the first tunable RF filter path 66 is a first RF transmit filter, such that the RF system control circuitry 56 provides the first transmit signal TX1 to the RF transmit circuitry 64, which processes the first transmit signal TX1 to provide a first upstream RF transmit signal TU1 to the first tunable RF filter path 66. Similarly, the second tunable RF filter path 68 is a second RF transmit filter, such that the RF system control circuitry 56 provides a second transmit signal TX2 to the RF transmit circuitry 64, which processes the second transmit signal TX2 to provide a second upstream RF transmit signal TU2 to the second tunable RF filter path 68.

The RF transmit circuitry 64 may include up-conversion circuitry, amplification circuitry, power supply circuitry, filtering circuitry, switching circuitry, combining circuitry, splitting circuitry, dividing circuitry, clocking circuitry, the like, or any combination thereof. The first tunable RF filter path 66 receives and filters the first upstream RF transmit signal TU1 to provide the first filtered RF transmit signal TF1, which is transmitted via the first common connection node 74 by the first RF antenna 16. Similarly, the second tunable RF filter path 68 receives and filters the second upstream RF transmit signal TU2 to provide a second filtered RF transmit signal TF2, which is transmitted via the first common connection node 74 by the first RF antenna 16.

In one embodiment of the RF communications circuitry 54, the first tunable RF filter path 66 and the second tunable RF filter path 68 do not significantly load one another at frequencies of interest. As such, by directly coupling the first tunable RF filter path 66 and the second tunable RF filter path 68 to the first common connection node 74; front-end RF switching elements may be avoided, thereby reducing cost, size, and non-linearity; and increasing efficiency and flexibility of the RF communications circuitry 54.

In this regard, in one embodiment of the first tunable RF filter path 66 and the second tunable RF filter path 68, each of the first tunable RF filter path 66 and the second tunable RF filter path 68 is a bandpass filter having a unique center frequency. As such, the first filter parameter of each of the first tunable RF filter path 66 and the second tunable RF filter path 68 is a unique center frequency.

In an alternate embodiment of the first tunable RF filter path 66 and the second tunable RF filter path 68, one of the first tunable RF filter path 66 and the second tunable RF filter path 68 is a lowpass filter, and another of the first tunable RF filter path 66 and the second tunable RF filter path 68 is a highpass filter. As such, the first filter parameter of each of the first tunable RF filter path 66 and the second tunable RF filter path 68 is a break frequency.

In an additional embodiment of the first tunable RF filter path 66 and the second tunable RF filter path 68, one of the first tunable RF filter path 66 and the second tunable RF filter path 68 is a lowpass filter, and another of the first tunable RF filter path 66 and the second tunable RF filter path 68 is a bandpass filter. As such, the first filter parameter of one of the first tunable RF filter path 66 and the second tunable RF filter path 68 is a center frequency, and the first filter parameter of another of the first tunable RF filter path 66 and the second tunable RF filter path 68 is a break frequency.

In an additional embodiment of the first tunable RF filter path 66 and the second tunable RF filter path 68, one of the first tunable RF filter path 66 and the second tunable RF filter path 68 is a highpass filter, and another of the first tunable RF filter path 66 and the second tunable RF filter path 68 is a bandpass filter. As such, the first filter parameter of one of the first tunable RF filter path 66 and the second tunable RF filter path 68 is a center frequency, and the first filter parameter of another of the first tunable RF filter path 66 and the second tunable RF filter path 68 is a break frequency.

In one embodiment of the RF communications circuitry 54, the RF communications circuitry 54 is a transmit only CA system, such that the first tunable RF filter path 66, which is the first RF transmit filter, and the second tunable RF filter path 68, which is the second RF transmit filter, simultaneously receive and filter the first upstream RF transmit signal TU1 and the second upstream RF transmit signal TU2, respectively, to simultaneously provide the first filtered RF transmit signal TF1 and the second filtered RF transmit signal TF2, respectively, via the first common connection node 74. As such, the first RF filter structure 60 functions as a multiplexer. In this regard, each of the first filtered RF transmit signal TF1 and the second filtered RF transmit signal TF2 has a unique carrier frequency. Using transmit CA may increase an effective transmit bandwidth of the RF communications circuitry 54.

In another embodiment of the RF communications circuitry 54, the RF communications circuitry 54 is a transmit only communications system, such that the first tunable RF filter path 66, which is the first RF transmit filter, and the second tunable RF filter path 68, which is the second RF transmit filter, do not simultaneously receive and filter the first upstream RF transmit signal TU1 and the second upstream RF transmit signal TU2, respectively. As such, the first filtered RF transmit signal TF1 and the second filtered RF transmit signal TF2 are nonsimultaneous signals. Each of the first filtered RF transmit signal TF1 and the second filtered RF transmit signal TF2 may be associated with a unique RF communications band.

FIGS. 9A and 9B are graphs illustrating filtering characteristics of the first tunable RF filter path 66 and the second tunable RF filter path 68, respectively, illustrated in FIG. 8 according to an additional embodiment of the first tunable RF filter path 66 and the second tunable RF filter path 68, respectively. FIG. 9A shows a frequency response curve 100 of the first tunable RF filter path 66 and FIG. 9B shows a frequency response curve 102 of the second tunable RF filter path 68. The first tunable RF filter path 66 and the second tunable RF filter path 68 are both bandpass filters having the frequency response curves 100, 102 illustrated in FIGS. 9A and 9B, respectively. In this regard, the first tunable RF filter path 66 and the second tunable RF filter path 68 can be directly coupled to one another via the first common connection node 74 (FIG. 8) without interfering with one another.

FIGS. 10A and 10B are graphs illustrating filtering characteristics of the first traditional RF duplexer 30 and the second traditional RF duplexer 36, respectively, illustrated in FIG. 3 according to the prior art. FIG. 10A shows a frequency response curve 104 of the first traditional RF duplexer 30 and FIG. 10B shows a frequency response curve 106 of the second traditional RF duplexer 36. There is interference 108 between the frequency response curve 104 of the first traditional RF duplexer 30 and the frequency response curve 106 of the second traditional RF duplexer 36 as shown in FIGS. 10A and 10B. In this regard, the first traditional RF duplexer 30 and the second traditional RF duplexer 36 cannot be directly coupled to one another without interfering with one another. To avoid interference between different filters, traditional systems use RF switches to disconnect unused filters.

FIG. 11 shows the RF communications circuitry 54 according to one embodiment of the RF communications circuitry 54. The RF communications circuitry 54 illustrated in FIG. 11 is similar to the RF communications circuitry 54 illustrated in FIG. 8, except in the RF communications circuitry 54 illustrated in FIG. 11, the RF front-end circuitry 58 further includes the RF receive circuitry 62 and the first RF filter structure 60 further includes a third tunable RF filter path 110 and a fourth tunable RF filter path 112. Additionally, the RF front-end circuitry 58 has the first connection node 70, the second connection node 72, the first common connection node 74, a third connection node 114 and a fourth connection node 116, such that all of the first connection node 70, the second connection node 72, the first common connection node 74, the third connection node 114 and the fourth connection node 116 are external to the first RF filter structure 60. In an alternate of the RF front-end circuitry 58, any or all of the first connection node 70, the second connection node 72, the first common connection node 74, a third connection node 114 and a fourth connection node 116 are internal to the first RF filter structure 60.

The RF front-end control circuitry 98 further provides a third filter control signal FCS3 to the third tunable RF filter path 110 and a fourth filter control signal FCS4 to the fourth tunable RF filter path 112 based on the front-end control signal FEC. In one embodiment of the RF communications circuitry 54, the control circuitry tunes a first filter parameter of the third tunable RF filter path 110 using the third filter control signal FCS3. Additionally, the control circuitry tunes a first filter parameter of the fourth tunable RF filter path 112 using the fourth filter control signal FCS4. In an additional embodiment of the RF communications circuitry 54, the control circuitry further tunes a second filter parameter of the third tunable RF filter path 110 using the third filter control signal FCS3; and the control circuitry further tunes a second filter parameter of the fourth tunable RF filter path 112 using the fourth filter control signal FCS4.

In one embodiment of the third tunable RF filter path 110, the third tunable RF filter path 110 includes a third pair (not shown) of weakly coupled resonators. In one embodiment of the fourth tunable RF filter path 112, the fourth tunable RF filter path 112 includes a fourth pair (not shown) of weakly coupled resonators.

In one embodiment of the third tunable RF filter path 110 and the fourth tunable RF filter path 112, the third tunable RF filter path 110 is directly coupled between the first common connection node 74 and the third connection node 114, and the fourth tunable RF filter path 112 is directly coupled between the fourth connection node 116 and the first common connection node 74. In another embodiment of the RF communications circuitry 54, the first RF antenna 16 is omitted. Additionally, the RF receive circuitry 62 is coupled between the third connection node 114 and the RF system control circuitry 56, and the RF receive circuitry 62 is further coupled between the fourth connection node 116 and the RF system control circuitry 56.

In one embodiment of the RF communications circuitry 54, the third tunable RF filter path 110 is the first RF receive filter, such that the first RF antenna 16 forwards a first received RF signal via the first common connection node 74 to provide the first upstream RF receive signal RU1 to the third tunable RF filter path 110, which receives and filters the first upstream RF receive signal RU1 to provide the first filtered RF receive signal RF1 to the RF receive circuitry 62. Additionally, the fourth tunable RF filter path 112 is a second RF receive filter, such that the first RF antenna 16 forwards a second received RF signal via the first common connection node 74 to provide the second upstream RF receive signal RU2 to the fourth tunable RF filter path 112, which receives and filters the second upstream RF receive signal RU2 to provide the second filtered RF receive signal RF2 to the RF receive circuitry 62.

The RF receive circuitry 62 may include down-conversion circuitry, amplification circuitry, power supply circuitry, filtering circuitry, switching circuitry, combining circuitry, splitting circuitry, dividing circuitry, clocking circuitry, the like, or any combination thereof. The RF receive circuitry 62 processes the first filtered RF receive signal RF1 to provide the first receive signal RX1 to the RF system control circuitry 56. Additionally, the RF receive circuitry 62 processes the second filtered RF receive signal RF2 to provide the second receive signal RX2 to the RF system control circuitry 56.

In one embodiment of the RF communications circuitry 54, the first tunable RF filter path 66, the second tunable RF filter path 68, the third tunable RF filter path 110, and the fourth tunable RF filter path 112 do not significantly load one another at frequencies of interest. As such, by directly coupling the first tunable RF filter path 66, the second tunable RF filter path 68, the third tunable RF filter path 110, and the fourth tunable RF filter path 112 to the first common connection node 74; front-end RF switching elements may be avoided, thereby reducing cost, size, and non-linearity; and increasing efficiency and flexibility of the RF communications circuitry 54.

In this regard, in one embodiment of the third tunable RF filter path 110 and the fourth tunable RF filter path 112, each of the third tunable RF filter path 110 and the fourth tunable RF filter path 112 is a bandpass filter having a unique center frequency. As such, the first filter parameter of each of the third tunable RF filter path 110 and the fourth tunable RF filter path 112 is a unique center frequency.

In an alternate embodiment of the third tunable RF filter path 110 and the fourth tunable RF filter path 112, one of the third tunable RF filter path 110 and the fourth tunable RF filter path 112 is a lowpass filter, and another of the third tunable RF filter path 110 and the fourth tunable RF filter path 112 is a highpass filter. As such, the first filter parameter of each of the third tunable RF filter path 110 and the fourth tunable RF filter path 112 is a break frequency.

In an additional embodiment of the third tunable RF filter path 110 and the fourth tunable RF filter path 112, one of the third tunable RF filter path 110 and the fourth tunable RF filter path 112 is a lowpass filter, and another of the third tunable RF filter path 110 and the fourth tunable RF filter path 112 is a bandpass filter. As such, the first filter parameter of one of the third tunable RF filter path 110 and the fourth tunable RF filter path 112 is a center frequency, and the first filter parameter of another of the third tunable RF filter path 110 and the fourth tunable RF filter path 112 is a break frequency.

In an additional embodiment of the third tunable RF filter path 110 and the fourth tunable RF filter path 112, one of the third tunable RF filter path 110 and the fourth tunable RF filter path 112 is a highpass filter, and another of the third tunable RF filter path 110 and the fourth tunable RF filter path 112 is a bandpass filter. As such, the first filter parameter of one of the third tunable RF filter path 110 and the fourth tunable RF filter path 112 is a center frequency, and the first filter parameter of another of the third tunable RF filter path 110 and the fourth tunable RF filter path 112 is a break frequency.

In one embodiment of the RF communications circuitry 54, the RF communications circuitry 54 is a CA system, such that the third tunable RF filter path 110, which is the first RF receive filter, and the fourth tunable RF filter path 112, which is the second RF receive filter, simultaneously receive and filter the first upstream RF receive signal RU1 and the second upstream RF receive signal RU2, respectively, via the first common connection node 74. As such, the first RF filter structure 60 functions as a de-multiplexer using the third tunable RF filter path 110 and the fourth tunable RF filter path 112. In one embodiment of the first RF filter structure 60, the first RF filter structure 60 further functions as a multiplexer using the first tunable RF filter path 66 and the second tunable RF filter path 68. In this regard, each of the first upstream RF receive signal RU1 and the second upstream RF receive signal RU2 has a unique carrier frequency.

In another embodiment of the RF communications circuitry 54, the RF communications circuitry 54 is a receive communications system, such that the third tunable RF filter path 110, which is the first RF receive filter, and the fourth tunable RF filter path 112, which is the second RF receive filter, do not simultaneously receive and filter the first upstream RF receive signal RU1 and the second upstream RF receive signal RU2, respectively. As such, the first upstream RF receive signal RU1 and the second upstream RF receive signal RU2 are nonsimultaneous signals. Each of the first upstream RF receive signal RU1 and the second upstream RF receive signal RU2 may be associated with a unique RF communications band.

FIG. 12 shows the RF communications circuitry 54 according to an alternate embodiment of the RF communications circuitry 54. The RF communications circuitry 54 illustrated in FIG. 12 is similar to the RF communications circuitry 54 illustrated in FIG. 11, except the RF communications circuitry 54 illustrated in FIG. 12 further includes the second RF antenna 32. Additionally, the RF front-end circuitry 58 further includes a second common connection node 118 and a second RF filter structure 120. The third tunable RF filter path 110 and the fourth tunable RF filter path 112 are included in the second RF filter structure 120 instead of being included in the first RF filter structure 60. Instead of being coupled to the first common connection node 74, the third tunable RF filter path 110 and the fourth tunable RF filter path 112 are coupled to the second common connection node 118. In one embodiment of the third tunable RF filter path 110 and the fourth tunable RF filter path 112, the third tunable RF filter path 110 and the fourth tunable RF filter path 112 are directly coupled to the second common connection node 118. In one embodiment of the RF communications circuitry 54, the second RF antenna 32 is coupled to the second common connection node 118.

FIG. 13 shows the RF communications circuitry 54 according to an additional embodiment of the RF communications circuitry 54. The RF communications circuitry 54 illustrated in FIG. 13 is similar to the RF communications circuitry 54 illustrated in FIG. 12, except in the RF communications circuitry 54 illustrated in FIG. 13, the RF front-end control circuitry 98 provides a front-end status signal FES to the RF system control circuitry 56. Additionally, the RF front-end control circuitry 98 provides a first calibration control signal CCS1 and up to and including an NTH calibration control signal CCSN to the first RF filter structure 60. The RF front-end control circuitry 98 provides a PTH calibration control signal CCSP and up to and including an XTH calibration control signal CCSX to the second RF filter structure 120. Details of the first RF filter structure 60 and the second RF filter structure 120 are not shown to simplify FIG. 13.

The first RF filter structure 60 provides a first calibration status signal CSS1 and up to and including a QTH calibration status signal CSSQ to the RF front-end control circuitry 98. The second RF filter structure 120 provides an RTH calibration status signal CSSR and up to and including a YTH calibration status signal CSSY to the RF front-end control circuitry 98. In an alternate embodiment of the RF front-end circuitry 58, any or all of the NTH calibration control signal CCSN, the QTH calibration status signal CSSQ, the XTH calibration control signal CCSX, and the YTH calibration status signal CSSY are omitted.

In one embodiment of the RF front-end circuitry 58, the RF front-end circuitry 58 operates in one of a normal operating mode and a calibration mode. During the calibration mode, the RF front-end control circuitry 98 performs a calibration of the first RF filter structure 60, the second RF filter structure 120, or both. As such, the RF front-end control circuitry 98 provides any or all of the filter control signals FCS1, FCS2, FCS3, FCS4 and any or all of the calibration control signals CCS1, CCSN, CCSP, CCSX needed for calibration. Further, the RF front-end control circuitry 98 receives any or all of the calibration status signals CSS1, CSSQ, CSSR, CSSY needed for calibration.

During the normal operating mode, the RF front-end control circuitry 98 provides any or all of the filter control signals FCS1, FCS2, FCS3, FCS4 and any or all of the calibration control signals CCS1, CCSN, CCSP, CCSX needed for normal operation. Further, the RF front-end control circuitry 98 receives any or all of the calibration status signals CSS1, CSSQ, CSSR, CSSY needed for normal operation. Any or all of the calibration control signals CCS1, CCSN, CCSP, CCSX may be based on the front-end control signal FEC. The front-end status signal FES may be based on any or all of the calibration status signals CSS1, CSSQ, CSSR, CSSY. Further, during the normal operating mode, the RF front-end circuitry 58 processes signals as needed for normal operation. Other embodiments described in the present disclosure may be associated with normal operation.

The RF communications circuitry 54 illustrated in FIG. 13 includes the first RF antenna 16 and the second RF antenna 32. In general, the RF communications circuitry 54 is a multiple antenna system. A single-input single-output (SISO) antenna system is a system in which RF transmit signals may be transmitted from the first RF antenna 16 and RF receive signals may be received via the second RF antenna 32. In one embodiment of the RF communications circuitry 54, the antenna system in the RF communications circuitry 54 is a SISO antenna system, as illustrated in FIG. 13.

A single-input multiple-output (SIMO) antenna system is a system in which RF transmit signals may be simultaneously transmitted from the first RF antenna 16 and the second RF antenna 32, and RF receive signals may be received via the second RF antenna 32. In an alternate embodiment of the RF communications circuitry 54, the second RF filter structure 120 is coupled to the RF transmit circuitry 64, such that the antenna system in the RF communications circuitry 54 is a SIMO antenna system.

A multiple-input single-output (MISO) antenna system is a system in which RF transmit signals may be transmitted from the first RF antenna 16, and RF receive signals may be simultaneously received via the first RF antenna 16 and the second RF antenna 32. In an additional embodiment of the RF communications circuitry 54, the first RF filter structure 60 is coupled to the RF receive circuitry 62, such that the antenna system in the RF communications circuitry 54 is a MISO antenna system.

A multiple-input multiple-output (MIMO) antenna system is a system in which RF transmit signals may be simultaneously transmitted from the first RF antenna 16 and the second RF antenna 32, and RF receive signals may be simultaneously received via the first RF antenna 16 and the second RF antenna 32. In another embodiment of the RF communications circuitry 54, the second RF filter structure 120 is coupled to the RF transmit circuitry 64 and the first RF filter structure 60 is coupled to the RF receive circuitry 62, such that the antenna system in the RF communications circuitry 54 is a MIMO antenna system.

FIG. 14 shows the RF communications circuitry 54 according to another embodiment of the RF communications circuitry 54. The RF communications circuitry 54 illustrated in FIG. 14 is similar to the RF communications circuitry 54 illustrated in FIG. 11, except in the RF communications circuitry 54 illustrated in FIG. 14, the first RF filter structure 60 further includes a fifth tunable RF filter path 122 and a sixth tunable RF filter path 124, and the RF front-end circuitry 58 further includes a fifth connection node 126 and a sixth connection node 128. Additionally, the RF front-end control circuitry 98 shown in FIG. 11 is not shown in FIG. 14 to simplify FIG. 14.

In one embodiment of the fifth tunable RF filter path 122, the fifth tunable RF filter path 122 includes a fifth pair (not shown) of weakly coupled resonators. In one embodiment of the sixth tunable RF filter path 124, the sixth tunable RF filter path 124 includes a sixth pair (not shown) of weakly coupled resonators.

In one embodiment of the fifth tunable RF filter path 122 and the sixth tunable RF filter path 124, the fifth tunable RF filter path 122 is directly coupled between the first common connection node 74 and the fifth connection node 126, and the sixth tunable RF filter path 124 is directly coupled between the sixth connection node 128 and the first common connection node 74. In another embodiment of the RF communications circuitry 54, the first RF antenna 16 is omitted. Additionally, the RF receive circuitry 62 is further coupled between the sixth connection node 128 and the RF system control circuitry 56, and the RF transmit circuitry 64 is further coupled between the fifth connection node 126 and the RF system control circuitry 56.

In one embodiment of the RF communications circuitry 54, the sixth tunable RF filter path 124 is a third RF receive filter, such that the first RF antenna 16 forwards a third received RF signal via the first common connection node 74 to provide a third upstream RF receive signal RU3 to the sixth tunable RF filter path 124, which receives and filters the third upstream RF receive signal RU3 to provide a third filtered RF receive signal RF3 to the RF receive circuitry 62, which processes the third filtered RF receive signal RF3 to provide the third receive signal RX3 to the RF system control circuitry 56.

In one embodiment of the RF communications circuitry 54, the fifth tunable RF filter path 122 is a third RF transmit filter, such that the RF system control circuitry 56 provides a third transmit signal TX3 to the RF transmit circuitry 64, which processes the third transmit signal TX3 to provide a third upstream RF transmit signal TU3 to the fifth tunable RF filter path 122. The fifth tunable RF filter path 122 receives and filters the third upstream RF transmit signal TU3 to provide a third filtered RF transmit signal TF3, which is transmitted via the first common connection node 74 by the first RF antenna 16.

In one embodiment of the RF communications circuitry 54, the first tunable RF filter path 66, the second tunable RF filter path 68, the third tunable RF filter path 110, the fourth tunable RF filter path 112, the fifth tunable RF filter path 122, and the sixth tunable RF filter path 124 do not significantly load one another at frequencies of interest. Therefore, antenna switching circuitry 34, 42 (FIG. 3) may be avoided. As such, by directly coupling the first tunable RF filter path 66, the second tunable RF filter path 68, the third tunable RF filter path 110, the fourth tunable RF filter path 112, the fifth tunable RF filter path 122 and the sixth tunable RF filter path 124 to the first common connection node 74; front-end RF switching elements may be avoided, thereby reducing cost, size, and non-linearity; and increasing efficiency and flexibility of the RF communications circuitry 54.

In one embodiment of the RF communications circuitry 54, the RF communications circuitry 54 is an FDD communications system, such that each of the first tunable RF filter path 66, the second tunable RF filter path 68, the third tunable RF filter path 110, the fourth tunable RF filter path 112, the fifth tunable RF filter path 122, and the sixth tunable RF filter path 124 is a bandpass filter having a unique center frequency. As such, in one embodiment of the RF system control circuitry 56, the first filter parameter of each of the first tunable RF filter path 66, the second tunable RF filter path 68, the third tunable RF filter path 110, the fourth tunable RF filter path 112, the fifth tunable RF filter path 122, and the sixth tunable RF filter path 124 is a unique center frequency.

FIG. 15 shows the RF communications circuitry 54 according to a further embodiment of the RF communications circuitry 54. The RF communications circuitry 54 illustrated in FIG. 15 is similar to the RF communications circuitry 54 illustrated in FIG. 4, except in the RF communications circuitry 54 illustrated in FIG. 15, the RF front-end circuitry 58 further includes an RF antenna switch 130 and the third connection node 114. Additionally, the first RF filter structure 60 further includes the third tunable RF filter path 110. Instead of the first RF antenna 16 being directly coupled to the first common connection node 74, as illustrated in FIG. 4, the RF antenna switch 130 is coupled between the first RF antenna 16 and the first common connection node 74. As such, the first common connection node 74 is coupled to the first RF antenna 16 via the RF antenna switch 130. In this regard, the RF communications circuitry 54 is a hybrid RF communications system.

The RF antenna switch 130 has an antenna switch common connection node 132, an antenna switch first connection node 134, an antenna switch second connection node 136, and an antenna switch third connection node 138. The antenna switch common connection node 132 is coupled to the first RF antenna 16. In one embodiment of the RF antenna switch 130, the antenna switch common connection node 132 is directly coupled to the first RF antenna 16. The antenna switch first connection node 134 is coupled to the first common connection node 74. In one embodiment of the RF antenna switch 130, the antenna switch first connection node 134 is directly coupled to the first common connection node 74. The antenna switch second connection node 136 may be coupled to other circuitry (not shown). The antenna switch third connection node 138 may be coupled to other circuitry (not shown). In another embodiment of the RF antenna switch 130, the antenna switch third connection node 138 is omitted. In a further embodiment of the RF antenna switch 130, the RF antenna switch 130 has at least one additional connection node.

The RF system control circuitry 56 provides a switch control signal SCS to the RF antenna switch 130. As such, the RF system control circuitry 56 selects one of the antenna switch first connection node 134, the antenna switch second connection node 136, and the antenna switch third connection node 138 to be coupled to the antenna switch common connection node 132 using the switch control signal SCS.

The third tunable RF filter path 110 is directly coupled between the first common connection node 74 and the third connection node 114. In one embodiment of the RF communications circuitry 54, the third tunable RF filter path 110 is a second RF receive filter, such that the first RF antenna 16 forwards a received RF signal via the RF antenna switch 130 and the first common connection node 74 to provide the second upstream RF receive signal RU2 to the third tunable RF filter path 110, which receives and filters the second upstream RF receive signal RU2 to provide the second filtered RF receive signal RF2 to the RF receive circuitry 62. The RF receive circuitry 62 processes the second filtered RF receive signal RF2 to provide a second receive signal RX2 to the RF system control circuitry 56.

The RF system control circuitry 56 further provides the third filter control signal FCS3. As such, in one embodiment of the RF communications circuitry 54, the RF system control circuitry 56 tunes a first filter parameter of the third tunable RF filter path 110 using the third filter control signal FCS3. In one embodiment of the RF communications circuitry 54, the RF communications circuitry 54 uses the second tunable RF filter path 68 and the third tunable RF filter path 110 to provide receive CA. In an alternate embodiment of the RF communications circuitry 54, tunable RF filters allow for sharing a signal path to provide both an FDD signal path and a TDD signal path, thereby lowering front-end complexity.

FIG. 16 shows the RF communications circuitry 54 according to one embodiment of the RF communications circuitry 54. The RF communications circuitry 54 illustrated in FIG. 16 is similar to the RF communications circuitry 54 illustrated in FIG. 15, except in the RF communications circuitry 54 illustrated in FIG. 16, the third tunable RF filter path 110 is omitted. Additionally, in one embodiment of the RF communications circuitry 54, the RF receive circuitry 62, the RF transmit circuitry 64, and the first RF filter structure 60 are all broadband devices. As such, the RF communications circuitry 54 is broadband circuitry capable of processing RF signals having wide frequency ranges.

FIG. 17 shows the RF communications circuitry 54 according to an alternate embodiment of the RF communications circuitry 54. The RF communications circuitry 54 illustrated in FIG. 17 is similar to the RF communications circuitry 54 illustrated in FIG. 16, except in the RF communications circuitry 54 illustrated in FIG. 17, the RF receive circuitry 62 is omitted and the RF front-end circuitry 58 further includes a first RF front-end circuit 140, a second RF front-end circuit 142, and a third RF front-end circuit 144.

The first RF front-end circuit 140 includes the RF transmit circuitry 64. The second RF front-end circuit 142 includes the first RF filter structure 60, the first connection node 70, the second connection node 72, and the first common connection node 74. The third RF front-end circuit 144 includes the RF antenna switch 130. In one embodiment of the first RF front-end circuit 140, the first RF front-end circuit 140 is a first RF front-end integrated circuit (IC). In one embodiment of the second RF front-end circuit 142, the second RF front-end circuit 142 is a second RF front-end IC. In one embodiment of the third RF front-end circuit 144, the third RF front-end circuit 144 is a third RF front-end IC.

FIG. 18 shows the RF communications circuitry 54 according to an additional embodiment of the RF communications circuitry 54. The RF communications circuitry 54 illustrated in FIG. 18 is similar to the RF communications circuitry 54 illustrated in FIG. 16, except in the RF communications circuitry 54 illustrated in FIG. 18, the RF receive circuitry 62 is omitted and the RF front-end circuitry 58 further includes the first RF front-end circuit 140 and the second RF front-end circuit 142.

The first RF front-end circuit 140 includes the RF transmit circuitry 64. The second RF front-end circuit 142 includes the first RF filter structure 60, the RF antenna switch 130, the first connection node 70, the second connection node 72, and the first common connection node 74. In one embodiment of the first RF front-end circuit 140, the first RF front-end circuit 140 is the first RF front-end IC. In one embodiment of the second RF front-end circuit 142, the second RF front-end circuit 142 is the second RF front-end IC.

FIG. 19 shows the RF communications circuitry 54 according to another embodiment of the RF communications circuitry 54. The RF communications circuitry 54 illustrated in FIG. 19 is similar to the RF communications circuitry 54 illustrated in FIG. 16, except in the RF communications circuitry 54 illustrated in FIG. 19, the RF receive circuitry 62 is omitted and the RF front-end circuitry 58 further includes the first RF front-end circuit 140.

The first RF front-end circuit 140 includes the RF transmit circuitry 64, the first RF filter structure 60, the RF antenna switch 130, the first connection node 70, the second connection node 72, and the first common connection node 74. In one embodiment of the first RF front-end circuit 140, the first RF front-end circuit 140 is the first RF front-end IC.

FIG. 20 shows the RF communications circuitry 54 according to a further embodiment of the RF communications circuitry 54. The RF communications circuitry 54 illustrated in FIG. 20 is a TDD system, which is capable of transmitting and receiving RF signals, but not simultaneously. As such, the RF communications circuitry 54 illustrated in FIG. 20 is similar to the RF communications circuitry 54 illustrated in FIG. 4, except in the RF communications circuitry 54 illustrated in FIG. 20, the second tunable RF filter path 68 and the second connection node 72 are omitted, and the RF front-end circuitry 58 further includes an RF transmit/receive switch 146 coupled between the first tunable RF filter path 66 and the RF receive circuitry 62, and further coupled between the first tunable RF filter path 66 and the RF transmit circuitry 64.

Since the RF communications circuitry 54 does not simultaneously transmit and receive RF signals, the first tunable RF filter path 66 provides front-end transmit filtering when the RF communications circuitry 54 is transmitting RF signals and the first tunable RF filter path 66 provides front-end receive filtering when the RF communications circuitry 54 is receiving RF signals. In this regard, the first tunable RF filter path 66 processes half-duplex signals.

The RF transmit/receive switch 146 has a transmit/receive switch common connection node 148, a transmit/receive switch first connection node 150, and a transmit/receive switch second connection node 152. The RF receive circuitry 62 is coupled between the RF system control circuitry 56 and the transmit/receive switch second connection node 152. The RF transmit circuitry 64 is coupled between the RF system control circuitry 56 and the transmit/receive switch first connection node 150. The first connection node 70 is coupled to the transmit/receive switch common connection node 148.

The RF system control circuitry 56 provides a switch control signal SCS to the RF transmit/receive switch 146. As such, the RF system control circuitry 56 selects either the transmit/receive switch first connection node 150 or the transmit/receive switch second connection node 152 to be coupled to the transmit/receive switch common connection node 148 using the switch control signal SCS. Therefore, when the RF communications circuitry 54 is transmitting RF signals, the RF transmit circuitry 64 is coupled to the first tunable RF filter path 66 and the RF receive circuitry 62 is not coupled to the first tunable RF filter path 66. Conversely, when the RF communications circuitry 54 is receiving RF signals, the RF receive circuitry 62 is coupled to the first tunable RF filter path 66 and the RF transmit circuitry 64 is not coupled to the first tunable RF filter path 66.

FIG. 21 illustrates an exemplary embodiment of the first RF filter structure 60. The first RF filter structure 60 includes a plurality of resonators (referred to generically as elements R and specifically as elements R(i,j), where an integer i indicates a row position and an integer j indicates a column position, where 1≦i≦M, 1≦j≦N and M is any integer greater than 1 and N is any integer greater than to 1. It should be noted that in alternative embodiments the number of resonators R in each row and column may be the same or different). The first tunable RF filter path 66 includes row 1 of weakly coupled resonators R(1,1), R(1,2) through (R(1,N). All of the weakly coupled resonators R(1,1), R(1,2) through (R(1,N) are weakly coupled to one another. Furthermore, the first tunable RF filter path 66 is electrically connected between terminal 200 and terminal 202. In this manner, the first tunable RF filter path 66 is configured to receive RF signals and output filtered RF signals. The second tunable RF filter path 68 includes row M of weakly coupled resonators R(M,1), R(M,2) through R(M,N). All of the weakly coupled resonators R(M,1), R(M,2) through R(M,N) are weakly coupled to one another. Furthermore, the second tunable RF filter path 68 is electrically connected between terminal 204 and terminal 206. In this manner, the second tunable RF filter path 68 is configured to receive RF signals and output filtered RF signals. It should be noted that the first RF filter structure 60 may include any number of tunable RF filter paths, such as, for example, the third tunable RF filter path 110, the fourth tunable RF filter path 112, the fifth tunable RF filter path 122, and the sixth tunable RF filter path 124, described above with respect to FIGS. 11-14. Each of the resonators R may be a tunable resonator, which allows for a resonant frequency of each of the resonators R to be varied to along a frequency range. In some embodiments, not all of the couplings between the resonators R are weak. A hybrid architecture having at least one pair of weakly coupled resonators R and strongly or moderately coupled resonators R is also possible.

Cross-coupling capacitive structures C are electrically connected to and between the resonators R. In this embodiment, each of the cross-coupling capacitive structures C is a variable cross-coupling capacitive structure, such as a varactor or an array of capacitors. To be independent, the magnetic couplings may be negligible. Alternatively, the cross-coupling capacitive structures C may simply be provided by a capacitor with a fixed capacitance. With regard to the exemplary embodiment shown in FIG. 21, the tunable RF filter paths of the first RF filter structure 60 are independent of one another. As such, the first tunable RF filter path 66 and the second tunable RF filter path 68 are independent of one another and thus do not have cross-coupling capacitive structures C between their resonators. Thus, in this embodiment, the cross-coupling capacitive structures C do not connect any of the weakly coupled resonators R(1,1), R(1,2) through (R(1,N) to any of the weakly coupled resonators R(M,1), R(M,2) through (R(M,N). This provides increased isolation between the first tunable RF filter path 66 and the second tunable RF filter path 68. In general, energy transfer between two weakly coupled resonators R in the first tunable RF filter path 66 and the second tunable RF filter path 68 may be provided by multiple energy transfer components. For example, energy may be transferred between the resonators R only through mutual magnetic coupling, only through mutual electric coupling, or through both mutual electric coupling and mutual magnetic coupling. Ideally, all of the mutual coupling coefficients are provided as designed, but in practice, the mutual coupling coefficients also be the result of parasitics. The inductors of the resonators R may also have magnetic coupling between them. A total coupling between the resonators R is given by the sum of magnetic and electric coupling.

In order to provide the transfer functions of the tunable RF filter paths 66, 68 with high out-of-band attenuation and a relatively low filter order, the tunable RF filter paths 66, 68 are configured to adjust notches in the transfer function, which are provided by the resonators R within the tunable RF filter paths 66, 68. The notches can be provided using parallel tanks connected in series or in shunt along a signal path of the first tunable RF filter path 66. To provide the notches, the parallel tanks operate approximately as an open circuit or as short circuits at certain frequencies. The notches can also be provided using multi-signal path cancellation. In this case, the tunable RF filter paths 66, 68 may be smaller and/or have fewer inductors. To tune the total mutual coupling coefficients between the resonators R towards a desired value, the tunable RF filter paths 66, 68 are configured to vary variable electric coupling coefficients so that parasitic couplings between the resonators R in the tunable RF filter paths 66, 68 are absorbed into a desired frequency transfer function.

FIG. 22 illustrates an exemplary embodiment of the first tunable RF filter path 66 in the first RF filter structure 60 shown in FIG. 21. While the exemplary embodiment shown in FIG. 22 is of the first tunable RF filter path 66, any of the tunable RF filter paths shown in the first RF filter structure 60 of

FIG. 21 may be arranged in accordance with the exemplary embodiment shown in FIG. 22. The first tunable RF filter path 66 shown in FIG. 22 includes an embodiment of the resonator R(1,1) and an embodiment of the resonator R(1,2). The resonator R(1,1) and the resonator R(1,2) are weakly coupled to one another. More specifically, the resonator R(1,1) includes an inductor 208 and a capacitive structure 210. The resonator R(1,2) includes an inductor 212, a capacitive structure 214, and a capacitive structure 216.

The resonator R(1,1) and the resonator R(1,2) are a pair of weakly coupled resonators. The resonator R(1,1) and the resonator R(1,2) are weakly coupled by providing the inductor 208 and the inductor 212 such that the inductor 208 and the inductor 212 are weakly magnetically coupled. Although the resonator R(1,1) and the resonator R(1,2) are weakly coupled, the inductor 212 has a maximum lateral width and a displacement between the inductor 208 and the inductor 212 is less than or equal to half the maximum lateral width of the inductor 212. As such, the inductor 208 and the inductor 212 are relatively close to one another. The displacement between the inductor 208 and the inductor 212 may be measured from a geometric centroid of the inductor 208 to a geometric centroid of the inductor 212. The maximum lateral width may be a maximum dimension of the inductor 212 along a plane defined by its largest winding. The weak coupling between the inductor 208 and the inductor 212 is obtained through topological techniques. For example, the inductor 208 and the inductor 212 may be fully or partially aligned, where winding(s) of the inductor 208 and winding(s) of the inductor 212 are configured to provide weak coupling through cancellation. Alternatively or additionally, a plane defining an orientation of the winding(s) of the inductor 208 and a plane defining an orientation of the winding(s) of the inductor 212 may be fully or partially orthogonal to one another. Some of the magnetic couplings between the resonators R can be unidirectional (passive or active). This can significantly improve isolation (e.g., transmit and receive isolation in duplexers).

To maximize the quality (Q) factor of the tunable RF filter paths 66 through 68, most of the total mutual coupling should be realized magnetically, and only fine-tuning is provided electrically. This also helps to reduce common-mode signal transfer in the differential resonators and thus keeps the Q factor high. While the magnetic coupling can be adjusted only statically, with a new layout design, the electric coupling can be tuned on the fly (after fabrication). The filter characteristics (e.g., bias network structure, resonator capacitance) can be adjusted based on given coupling coefficients to maximize filter performance.

To provide a tuning range to tune a transfer function of the first tunable RF filter path 66 and provide a fast roll-off from a low-frequency side to a high-frequency side of the transfer function, the first tunable RF filter path 66 is configured to change a sign of a total mutual coupling coefficient between the resonator R(1,1) and the resonator R(1,2). Accordingly, the first tunable RF filter path 66 includes a cross-coupling capacitive structure C(P1) and a cross-coupling capacitive structure C(N1). The cross-coupling capacitive structure C(P1) and the cross-coupling capacitive structure C(N1) are embodiments of the cross-coupling capacitive structures C described above with regard to FIG. 21. As shown in FIG. 22, the cross-coupling capacitive structure C(P1) is electrically connected between the resonator R(1,1) and the resonator R(1,2) so as to provide a positive coupling coefficient between the resonator R(1,1) and the resonator R(1,2). The cross-coupling capacitive structure C(P1) is a variable cross-coupling capacitive structure configured to vary the positive coupling coefficient provided between the resonator R(1,1) and the resonator R(1,2). The cross-coupling capacitive structure C(N1) is electrically connected between the resonator R(1,1) and the resonator R(1,2) so as to provide a negative coupling coefficient between the resonator R(1,1) and the resonator R(1,2). The cross-coupling capacitive structure C(N1) is a variable cross-coupling capacitive structure configured to vary the negative coupling coefficient provided between the resonator R(1,1) and the resonator R(1,2). The arrangement of the cross-coupling capacitive structure C(P1) and the cross-coupling capacitive structure C(N1) shown in FIG. 22 is a V-bridge structure. In alternative embodiments, some or all of the cross-coupling capacitive structures is fixed (not variable).

In the resonator R(1,1), the inductor 208 and the capacitive structure 210 are electrically connected in parallel. More specifically, the inductor 208 has an end 217 and an end 218, which are disposed opposite to one another. The ends 217, 218 are each electrically connected to the capacitive structure 210, which is grounded. Thus, the resonator R(1,1) is a single-ended resonator. On the other hand, the inductor 212 is electrically connected between the capacitive structure 214 and the capacitive structure 216. More specifically, the inductor 212 has an end 220 and an end 222, which are disposed opposite to one another. The end 220 is electrically connected to the capacitive structure 214 and the end 222 is electrically connected to the capacitive structure 216. Both the capacitive structure 214 and the capacitive structure 216 are grounded. Thus, the resonator R(1,2) is a differential resonator. In an alternative, an inductor with a center tap can be used. The tap can be connected to ground and only a single capacitive structure can be used. In yet another embodiment, both an inductor and a capacitive structure may have a center tap that is grounded. In still another embodiment, neither the inductor nor the capacitive structure may have a grounded center tap.

The inductor 208 is magnetically coupled to the inductor 212 such that an RF signal received at the end 217 of the inductor 208 with a voltage polarity (i.e., either a positive voltage polarity or a negative voltage polarity) results in a filtered RF signal being transmitted out the end 220 of the inductor 212 with the same voltage polarity. Also, the inductor 212 is magnetically coupled to the inductor 208 such that an RF signal received at the end 220 of the inductor 212 with a voltage polarity (i.e., either a positive voltage polarity or a negative voltage polarity) results in a filtered RF signal being transmitted out the end 217 of the inductor 208 with the same voltage polarity. This is indicated in FIG. 22 by the dot convention where a dot is placed at the end 217 of the inductor 208 and a dot is placed at the end 220 of the inductor 212. By using two independent and adjustable coupling coefficients (i.e., the positive coupling coefficient and the negative coupling coefficient) with the resonator R(1,2) (i.e., the differential resonator), the transfer function of the first tunable RF filter path 66 is provided so as to be fully adjustable. More specifically, the inductors 208, 212 may be magnetically coupled so as to have a low magnetic coupling coefficient through field cancellation, with the variable positive coupling coefficient and the variable negative coupling coefficient. In this case, the inductor 208 and the inductor 212 are arranged such that a mutual magnetic coupling between the inductor 208 and the inductor 212 cancel. Alternatively, the inductor 208 and the inductor 212 are arranged such that the inductor 212 reduces a mutual magnetic coupling coefficient of the inductor 208. With respect to the magnetic coupling coefficient, the variable positive coupling coefficient is a variable positive electric coupling coefficient and the variable negative coupling coefficient is a variable negative electric coupling coefficient. The variable positive electric coupling coefficient and the variable negative electric coupling coefficient oppose each other to create a tunable filter characteristic.

The resonator R(1,2) is operably associated with the resonator R(1,1) such that an energy transfer factor between the resonator R(1,1) and the resonator R(1,2) is less than 10%. A total mutual coupling between the resonator R(1,1) and the resonator R(1,2) is provided by a sum total of the mutual magnetic factor between the resonator R(1,1) and the resonator R(1,2) and the mutual electric coupling coefficients between the resonator R(1,1) and the resonator R(1,2). In this embodiment, the mutual magnetic coupling coefficient between the inductor 208 and the inductor 212 is a fixed mutual magnetic coupling coefficient. Although embodiments of the resonators R(1,1), R(1,2) may be provided so as to provide a variable magnetic coupling coefficient between the resonators R(1,1), R(1,2), embodiments of the resonators R(1,1), R(1,2) that provide variable magnetic couplings can be costly and difficult to realize. However, providing variable electric coupling coefficients (i.e., the variable positive electric coupling coefficient and the variable electric negative coupling coefficient) is easier and more economical. Thus, using the cross-coupling capacitive structure C(P1) and the cross-coupling capacitive structure C(N1) to provide the variable positive electric coupling coefficient and the variable electric negative coupling coefficient is an economical technique for providing a tunable filter characteristic between the resonators R(1,1), R(1,2). Furthermore, since the mutual magnetic coupling coefficient between the inductor 208 and the inductor 212 is fixed, the first tunable RF filter path 66 has lower insertion losses.

In the embodiment shown in FIG. 22, the inductor 208 and the 212 inductor are the same size. Alternatively, the inductor 208 and the inductor 212 may be different sizes. For example, the inductor 212 may be smaller than the inductor 208. By determining a distance between the inductor 208 and the inductor 212, the magnetic coupling coefficient between the inductor 208 and the inductor 212 can be set. With regard to the inductors 208, 212 shown in FIG. 22, the inductor 208 may be a folded inductor configured to generate a first confined magnetic field, while the inductor 212 may be a folded inductor configured to generate a second confined magnetic field. Magnetic field lines of the first confined magnetic field and of the second confined magnetic field that are external to the inductor 208 and inductor 212 are cancelled by opposing magnetic field lines in all directions. When the inductor 208 and the inductor 212 are folded inductors, the folded inductors can be stacked. This allows building the first tunable RF filter path 66 such that several inductors 208, 212 are stacked. Furthermore, this arrangement allows for a specially sized interconnect structure that electrically connects the inductors 208, 212 to the capacitive structure 210, the capacitive structure 214, the capacitive structure 216, the cross-coupling capacitive structure C(P1), and the cross-coupling capacitive structure C(N1). The specially sized interconnect increases the Q factor of the capacitive structure 210, the capacitive structure 214, the capacitive structure 216, the cross-coupling capacitive structure C(P1), and the cross-coupling capacitive structure C(N1), and allows for precise control of their variable capacitances. Weakly coupled filters can also be realized with planar field cancellation structures.

FIG. 23 illustrates an exemplary embodiment of the first tunable RF filter path 66 in the first RF filter structure 60 shown in FIG. 21. While the exemplary embodiment shown in FIG. 23 is of the first tunable RF filter path 66, any of the tunable RF filter paths shown in the first RF filter structure 60 of FIG. 21 may be arranged in accordance with the exemplary embodiment shown in FIG. 23. The first tunable RF filter path 66 shown in FIG. 23 includes an embodiment of the resonator R(1,1) and an embodiment of the resonator R(1,2). The resonator R(1,1) and the resonator R(1,2) are weakly coupled to one another. The embodiment of the resonator R(1,2) is the same as the embodiment of the resonator R(1,2) shown in FIG. 22. Thus, the resonator R(1,2) shown in FIG. 23 is a differential resonator that includes the inductor 212, the capacitive structure 214, and the capacitive structure 216. Additionally, like the embodiment of the resonator R(1,1) shown in FIG. 22, the embodiment of the resonator R(1,1) shown in FIG. 23 includes the inductor 208 and the capacitive structure 210. However, in this embodiment, the resonator R(1,1) shown in FIG. 23 is a differential resonator and further includes a capacitive structure 224. More specifically, the end 217 of the inductor 208 is electrically connected to the capacitive structure 210 and the end 218 of the inductor 208 is electrically connected to the capacitive structure 224. Both the capacitive structure 210 and the capacitive structure 224 are grounded. Like the capacitive structure 210, the capacitive structure 224 is also a variable capacitive structure, such as a programmable array of capacitors or a varactor. Alternatively, a center tap of an inductor may be grounded. In yet another embodiment, the inductor and a capacitive structure may be RF floating (a low-resistance connection to ground).

The resonator R(1,1) and the resonator R(1,2) are a pair of weakly coupled resonators. Like the first tunable RF filter path 66 shown in FIG. 22, the resonator R(1,1) and the resonator R(1,2) are weakly coupled by providing the inductor 208 and the inductor 212 such that the inductor 208 and the inductor 212 are weakly coupled. Thus, the inductor 208 and the inductor 212 may have a magnetic coupling coefficient that is less than or equal to approximately 0.3. Although the resonator R(1,1) and the resonator R(1,2) are weakly coupled, a displacement between the inductor 208 and the inductor 212 is less than or equal to half the maximum lateral width of the inductor 212. As such, the inductor 208 and the inductor 212 are relatively close to one another. The displacement between the inductor 208 and the inductor 212 may be measured from a geometric centroid of the inductor 208 to a geometric centroid of the inductor 212. The maximum lateral width may be a maximum dimension of the inductor 212 along a plane defined by its largest winding.

The weak coupling between the inductor 208 and the inductor 212 is obtained through topological techniques. For example, the inductor 208 and the inductor 212 may be fully or partially aligned, where winding(s) of the inductor 208 and winding(s) of the inductor 212 are configured to provide weak coupling through cancellation. Alternatively or additionally, a plane defining an orientation of the windings of the inductor 208 and a plane defining an orientation of the windings of the inductor 212 may be fully or partially orthogonal to one another.

The resonator R(1,2) is operably associated with the resonator R(1,1) such that an energy transfer factor between the resonator R(1,1) and the resonator R(1,2) is less than 10%. To provide a tuning range to tune a transfer function of the first tunable RF filter path 66 such to provide a fast roll-off from a low-frequency side to a high-frequency side requires changing a sign of the total mutual coupling coefficient between the resonator R(1,1) and the resonator R(1,2). Like the embodiment of the first tunable RF filter path 66 shown in FIG. 22, the first tunable RF filter path 66 shown in FIG. 23 includes the cross-coupling capacitive structure C(P1) and the cross-coupling capacitive structure C(N1). The cross-coupling capacitive structure C(P1) and the cross-coupling capacitive structure C(N1) are arranged in the same manner described above with respect to FIG. 22. However, in this embodiment, the first tunable RF filter path 66 shown in FIG. 23 also includes a cross-coupling capacitive structure C(P2) and a cross-coupling capacitive structure C(N2). The cross-coupling capacitive structure C(P2) and the cross-coupling capacitive structure C(N2) are also embodiments of the cross-coupling capacitive structures C described above with regard to FIG. 21.

As described above with respect to FIG. 22, the cross-coupling capacitive structure C(P1) is electrically connected between the resonator R(1,1) and the resonator R(1,2) so as to provide the positive coupling coefficient (i.e., the variable positive electric coupling coefficient) between the resonator R(1,1) and the resonator R(1,2). Also as described above with respect to FIG. 22, the cross-coupling capacitive structure C(N1) is electrically connected between the resonator R(1,1) and the resonator R(1,2) so as to provide the negative coupling coefficient (i.e., the variable negative electric coupling coefficient) between the resonator R(1,1) and the resonator R(1,2). With regard to the cross-coupling capacitive structure C(P2), the cross-coupling capacitive structure C(P2) is electrically connected between the resonator R(1,1) and the resonator R(1,2) so as to provide another positive coupling coefficient (i.e., another variable positive electric coupling coefficient) between the resonator R(1,1) and the resonator R(1,2). In this embodiment, the cross-coupling capacitive structure C(P2) is electrically connected between the end 218 of the inductor 208 and the end 222 of the inductor 212. The cross-coupling capacitive structure C(P2) is a variable cross-coupling capacitive structure configured to vary the other positive coupling coefficient (i.e., the other variable positive electric coupling coefficient) provided between the resonator R(1,1) and the resonator R(1,2). With regard to the cross-coupling capacitive structure C(N2), the cross-coupling capacitive structure C(N2) is electrically connected between the resonator R(1,1) and the resonator R(1,2) so as to provide another negative coupling coefficient (i.e., another variable negative electric coupling coefficient) between the resonator R(1,1) and the resonator R(1,2). In this embodiment, the cross-coupling capacitive structure C(N2) is electrically connected between the end 218 of the inductor 208 and the end 220 of the inductor 212. The cross-coupling capacitive structure C(N2) is a variable cross-coupling capacitive structure configured to vary the negative coupling coefficient (i.e., the other variable negative electric coupling coefficient) provided between the resonator R(1,1) and the resonator R(1,2). The arrangement of the cross-coupling capacitive structure C(P1), the cross-coupling capacitive structure C(N1), the cross-coupling capacitive structure C(P2), and the cross-coupling capacitive structure C(N2) shown in FIG. 23 is an X-bridge structure.

As shown in FIG. 23, the resonator R(1,2) is operably associated with the resonator R(1,1) such that an energy transfer factor between the resonator R(1,1) and the resonator R(1,2) is less than 10%. The total mutual coupling between the resonator R(1,1) and the resonator R(1,2) is provided by a sum total of the mutual magnetic factor between the resonator R(1,1) and the resonator R(1,2) and the mutual electric coupling coefficients between the resonator R(1,1) and the resonator R(1,2). Thus, in this embodiment, the total mutual coupling between the resonator R(1,1) and the resonator R(1,2) is provided by the sum total of the mutual magnetic coupling coefficient, the variable positive electric coupling coefficient provided by the cross-coupling capacitive structure C(P1), the variable negative electric coupling coefficient provided by the cross-coupling capacitive structure C(N1), the other variable positive electric coupling coefficient provided by the cross-coupling capacitive structure C(P2), and the other variable negative electric coupling coefficient provided by the cross-coupling capacitive structure C(N2).

FIG. 24 illustrates an exemplary embodiment of the first tunable RF filter path 66 in the first RF filter structure 60 shown in FIG. 21. While the exemplary embodiment shown in FIG. 24 is of the first tunable RF filter path 66, any of the tunable RF filter paths shown in the first RF filter structure 60 of FIG. 21 may be arranged in accordance with the exemplary embodiment shown in FIG. 24. The first tunable RF filter path 66 shown in FIG. 24 includes an embodiment of the resonator R(1,1) and an embodiment of the resonator R(1,2). The resonator R(1,1) and the resonator R(1,2) are weakly coupled to one another. The embodiment of the resonator R(1,1) is the same as the embodiment of the resonator R(1,1) shown in FIG. 22. Thus, the resonator R(1,1) shown in FIG. 24 is a single-ended resonator that includes the inductor 208 and the capacitive structure 210. Additionally, like the embodiment of the resonator R(1,2) shown in FIG. 22, the embodiment of the resonator R(1,2) shown in FIG. 24 includes the inductor 212 and the capacitive structure 214. However, in this embodiment, the resonator R(1,2) shown in FIG. 24 is a single-ended resonator. More specifically, the end 220 and the end 222 of the inductor 212 are each electrically connected to the capacitive structure 214, which is grounded.

The resonator R(1,1) and the resonator R(1,2) are a pair of weakly coupled resonators. Like the first tunable RF filter path 66 shown in FIG. 22, the resonator R(1,1) and the resonator R(1,2) are weakly coupled by providing the inductor 208 and the inductor 212 such that the inductor 208 and the inductor 212 are weakly coupled. Thus, the inductor 208 and the inductor 212 may have a magnetic coupling coefficient that is less than or equal to approximately 0.3. Although the resonator R(1,1) and the resonator R(1,2) are weakly coupled, the displacement between the inductor 208 and the inductor 212 is less than or equal to half the maximum lateral width of the inductor 212. As such, the inductor 208 and the inductor 212 are relatively close to one another. The displacement between the inductor 208 and the inductor 212 may be measured from the geometric centroid of the inductor 208 to the geometric centroid of the inductor 212. The maximum lateral width may be a maximum dimension of the inductor 212 along a plane defined by its largest winding. The weak coupling between the inductor 208 and the inductor 212 is obtained through topological techniques. For example, the inductor 208 and the inductor 212 may be fully or partially aligned, where winding(s) of the inductor 208 and winding(s) of the inductor 212 are configured to provide weak coupling through cancellation. Alternatively or additionally, a plane defining an orientation of the windings of the inductor 208 and a plane defining an orientation of the windings of the inductor 212 may be fully or partially orthogonal to one another.

The resonator R(1,2) is operably associated with the resonator R(1,1) such that an energy transfer factor between the resonator R(1,1) and the resonator R(1,2) is less than 10%. To provide a tuning range to tune a transfer function of the first tunable RF filter path 66 and provide a fast roll-off from a low-frequency side to a high-frequency side of the transfer function, the first tunable RF filter path 66 is configured to change a sign of a total mutual coupling coefficient between the resonator R(1,1) and the resonator R(1,2). However, in this embodiment, the first tunable RF filter path 66 shown in FIG. 24 only includes the cross-coupling capacitive structure C(P1), which is electrically connected between the end 217 of the inductor 208 and the end 220 of the inductor 212. As discussed above with respect to FIGS. 22 and 23, the cross-coupling capacitive structure C(P1) is a variable cross-coupling capacitive structure configured to vary the positive coupling coefficient (i.e., the variable positive electric coupling coefficient) provided between the resonator R(1,1) and the resonator R(1,2). Thus, in order to allow for the sign of the total mutual coupling coefficient between the resonator R(1,1) and the resonator R(1,2) to be changed, the inductor 208 and the inductor 212 are arranged so as to provide a fixed negative mutual magnetic coupling coefficient between the inductor 208 of the resonator R(1,1) and the inductor 212 of the resonator R(1,2). As such, varying the variable positive electric coupling coefficient allows for the sign of the total mutual coupling coefficient between the resonator R(1,1) and the resonator R(1,2) to be changed using only the cross-coupling capacitive structure C(P1).

As such, in this embodiment, the inductor 208 is magnetically coupled to the inductor 212 such that an RF signal received at the end 217 of the inductor 208 with a voltage polarity (i.e., either a positive voltage polarity or a negative voltage polarity) results in a filtered RF signal with the same voltage polarity being transmitted out the end 222 of the inductor 212. In addition, the inductor 212 is magnetically coupled to the inductor 208 such that an RF signal received at the end 222 of the inductor 212 with a voltage polarity (i.e., either a positive voltage polarity or a negative voltage polarity) results in a filtered RF signal with the same voltage polarity being transmitted out the end 217 of the inductor 208. This is indicated in FIG. 24 by the dot convention where a dot is placed at the end 217 of the inductor 208 and a dot is placed at the end 222 of the inductor 212. By using the fixed negative mutual magnetic coupling coefficient and the variable positive electric coupling coefficient, the transfer function of the first tunable RF filter path 66 is provided so to be fully adjustable. The arrangement of the cross-coupling capacitive structure C(P1) shown in FIG. 24 is a single positive bridge structure.

FIG. 25 illustrates another exemplary embodiment of the first tunable RF filter path 66 in the first RF filter structure 60 shown in FIG. 21. While the exemplary embodiment shown in FIG. 25 is of the first tunable RF filter path 66, any of the tunable RF filter paths shown in the first RF filter structure 60 of FIG. 21 may be arranged in accordance with the exemplary embodiment shown in FIG. 25. The first tunable RF filter path 66 shown in FIG. 25 includes an embodiment of the resonator R(1,1) and an embodiment of the resonator R(1,2). The resonator R(1,1) and the resonator R(1,2) are weakly coupled to one another. The embodiment of the resonator R(1,1) is the same as the embodiment of the resonator R(1,1) shown in FIG. 22. Thus, the resonator R(1,1) shown in FIG. 25 is a single-ended resonator that includes the inductor 208 and the capacitive structure 210, which are arranged in the same manner described above with respect to FIG. 22. Like the resonator R(1,2) shown in FIG. 24, the resonator R(1,2) shown in FIG. 25 is a single-ended resonator that includes the inductor 212 and the capacitive structure 214. However, the inductor 208 shown in FIG. 25 is magnetically coupled to the inductor 212 such that an RF signal received at the end 217 of the inductor 208 with a voltage polarity (i.e., either a positive voltage polarity or a negative voltage polarity) results in a filtered RF signal with the same voltage polarity being transmitted out the end 220 of the inductor 212. Also, the inductor 212 shown in FIG. 25 is magnetically coupled to the inductor 208 such that an RF signal received at the end 220 of the inductor 212 with a voltage polarity (i.e., either a positive voltage polarity or a negative voltage polarity) results in a filtered RF signal with the same voltage polarity being transmitted out the end 217 of the inductor 208. This is indicated in FIG. 25 by the dot convention where a dot is placed at the end 217 of the inductor 208 and a dot is placed at the end 220 of the inductor 212. In alternative embodiments, the resonator R(1,2) is a differential resonator. In yet another alternative embodiment, the resonator R(1,1) is a single-ended resonator while the resonator R(1,2) is a differential resonator.

The resonator R(1,1) and the resonator R(1,2) are a pair of weakly coupled resonators. Like the first tunable RF filter path 66 shown in FIG. 22, the resonator R(1,1) and the resonator R(1,2) are weakly coupled by providing the inductor 208 and the inductor 212 such that the inductor 208 and the inductor 212 are weakly coupled. Thus, the inductor 208 and the inductor 212 may have a fixed magnetic coupling coefficient that is less than or equal to approximately 0.3. Although the resonator R(1,1) and the resonator R(1,2) are weakly coupled, a displacement between the inductor 208 and the inductor 212 is less than or equal to half the maximum lateral width of the inductor 212. As such, the inductor 208 and the inductor 212 are relatively close to one another. The displacement between the inductor 208 and the inductor 212 may be measured from a geometric centroid of the inductor 208 to a geometric centroid of the inductor 212. The maximum lateral width may be a maximum dimension of the inductor 212 along a plane defined by its largest winding.

The weak coupling between the inductor 208 and the inductor 212 is obtained through topological techniques. For example, the inductor 208 and the inductor 212 may be fully or partially aligned, where winding(s) of the inductor 208 and winding(s) of the inductor 212 are configured to provide weak coupling through cancellation. Alternatively or additionally, a plane defining an orientation of the windings of the inductor 208 and a plane defining an orientation of the windings of the inductor 212 may be fully or partially orthogonal to one another.

The resonator R(1,2) is operably associated with the resonator R(1,1) such that an energy transfer factor between the resonator R(1,1) and the resonator R(1,2) is less than 10%. To provide a tuning range to tune the transfer function of the first tunable RF filter path 66 and to provide a fast roll-off from the low-frequency side to the high-frequency side of the transfer function, the first tunable RF filter path 66 is configured to change the sign of the total mutual coupling coefficient between the resonator R(1,1) and the resonator R(1,2). In this embodiment, the first tunable RF filter path 66 shown in FIG. 25 includes a cross-coupling capacitive structure C(PH1), a cross-coupling capacitive structure (CNH1), a cross-coupling capacitive structure C(I1), a cross-coupling capacitive structure C(PH2), and a cross-coupling capacitive structure C(NH2). The cross-coupling capacitive structure C(PH1), the cross-coupling capacitive structure (CNH1), the cross-coupling capacitive structure C(I1), the cross-coupling capacitive structure C(PH2), and the cross-coupling capacitive structure C(NH2) are also embodiments of the cross-coupling capacitive structures C described above with regard to FIG. 21.

The cross-coupling capacitive structure C(PH1) and the cross-coupling capacitive structure C(NH1) are arranged to form a first capacitive voltage divider. The first capacitive voltage divider is electrically connected to the resonator R(1,1). More specifically, the cross-coupling capacitive structure C(PH1) is electrically connected between the end 217 of the inductor 208 and a common connection node H1. The cross-coupling capacitive structure C(NH1) is electrically connected between the end 218 of the inductor 208 and the common connection node H1. Additionally, the cross-coupling capacitive structure C(PH2) and the cross-coupling capacitive structure C(NH2) are arranged to form a second capacitive voltage divider. The second capacitive voltage divider is electrically connected to the resonator R(1,2). More specifically, the cross-coupling capacitive structure C(PH2) is electrically connected between the end 220 of the inductor 212 and a common connection node H2. The cross-coupling capacitive structure C(NH2) is electrically connected between the end 222 of the inductor 212 and the common connection node H2. As shown in FIG. 25, the cross-coupling capacitive structure C(I1) is electrically connected between the first capacitive voltage divider and the second capacitive voltage divider. More specifically, the cross-coupling capacitive structure C(I1) is electrically connected between the common connection node H1 and the common connection node H2. The arrangement of the cross-coupling capacitive structure C(PH1), the cross-coupling capacitive structure C(NH1), the cross-coupling capacitive structure C(PH2), the cross-coupling capacitive structure C(NH2), and the cross-coupling capacitive structure C(I1) shown in FIG. 25 is an H-bridge structure. In an alternative H-bridge structure, the cross-coupling capacitive structure C(I1) is not provided and instead there is a short between the common connection node H1 and the common connection node H2. In addition, a center tap of the inductor 208 may be grounded and/or the common connection node H1 may be grounded. Finally, a high impedance to ground may be provided at the common connection node H1.

With regard to the first capacitive voltage divider, the cross-coupling capacitive structure C(PH1) is a variable cross-coupling capacitive structure configured to vary a first variable positive electric coupling coefficient provided between the resonator R(1,1) and the common connection node H1. The cross-coupling capacitive structure C(NH1) is a variable cross-coupling capacitive structure configured to vary a first variable negative electric coupling coefficient provided between the resonator R(1,1) and the common connection node H1. Thus, a mutual electric coupling coefficient of the resonator R(1,1) is approximately equal to the first variable positive electric coupling coefficient and the first variable negative electric coupling coefficient.

With regard to the second capacitive voltage divider, the cross-coupling capacitive structure C(PH2) is a variable cross-coupling capacitive structure configured to vary a second variable positive electric coupling coefficient provided between the resonator R(1,2) and the common connection node H2. The cross-coupling capacitive structure C(NH2) is a variable cross-coupling capacitive structure configured to vary a second variable negative electric coupling coefficient provided between the resonator R(1,2) and the common connection node H2. Thus, a mutual electric coupling coefficient of the resonator R(1,2) is approximately equal to the second variable positive electric coupling coefficient and the second variable negative electric coupling coefficient. Furthermore, the cross-coupling capacitive structure C(I1) is a variable cross-coupling capacitive structure configured to vary a first variable intermediate electric coupling coefficient provided between the common connection node H1 and the common connection node H2. The first tunable RF filter path 66 shown in FIG. 25 thus has a total mutual coupling coefficient between the resonator R(1,1) and the resonator R(1,2) equal to the sum total of the mutual magnetic coupling coefficient between the inductor 208 and the inductor 212, the mutual electric coupling coefficient of the resonator R(1,1), the mutual electric coupling coefficient of the resonator R(1,2), and the first variable intermediate electric coupling coefficient provided between the common connection node H1 and the common connection node H2. In alternative embodiments, cross-coupling capacitive structures with fixed capacitances are provided.

In one embodiment, the cross-coupling capacitive structure C(PH1), the cross-coupling capacitive structure C(NH1), the cross-coupling capacitive structure C(PH2), the cross-coupling capacitive structure C(NH2), and the cross-coupling capacitive structure C(I1) may each be provided as a varactor. However, the cross-coupling capacitive structure C(PH1), the cross-coupling capacitive structure C(NH1), the cross-coupling capacitive structure C(PH2), the cross-coupling capacitive structure C(NH2), and the cross-coupling capacitive structure C(I1) may each be provided as a programmable array of capacitors in order to reduce insertion losses and improve linearity. The cross-coupling capacitive structure C(PH1), the cross-coupling capacitive structure C(NH1), the cross-coupling capacitive structure C(PH2), the cross-coupling capacitive structure C(NH2), and the cross-coupling capacitive structure C(I1) can also be any combination of suitable variable cross-coupling capacitive structures, such as combinations of varactors and programmable arrays of capacitors. Although the H-bridge structure can provide good linearity and low insertion losses, the H-bridge structure can also suffer from common-mode signal transfer.

FIG. 26 illustrates yet another exemplary embodiment of the first tunable RF filter path 66 in the first RF filter structure 60 shown in FIG. 21. While the exemplary embodiment shown in FIG. 26 is of the first tunable RF filter path 66, any of the tunable RF filter paths shown in the first RF filter structure 60 of FIG. 21 may be arranged in accordance with the exemplary embodiment shown in FIG. 26. The first tunable RF filter path 66 shown in FIG. 26 can be used to ameliorate the common-mode signal transfer of the H-bridge structure shown in FIG. 25. More specifically, the first tunable RF filter path 66 shown in FIG. 26 includes the same embodiment of the resonator R(1,1) and the same embodiment of the resonator R(1,2) described above with respect to FIG. 25. Furthermore, the first tunable RF filter path 66 shown in FIG. 26 includes the first capacitive voltage divider with the cross-coupling capacitive structure C(PH1) and the cross-coupling capacitive structure C(NH1) described above with respect to FIG. 25, the second capacitive voltage divider with the cross-coupling capacitive structure C(PH2) and the cross-coupling capacitive structure (CNH2) described above with respect to FIG. 25, and the cross-coupling capacitive structure C(I1) described above with respect to FIG. 25. However, in this embodiment, the first tunable RF filter path 66 shown in FIG. 26 also includes a cross-coupling capacitive structure C(PH3), a cross-coupling capacitive structure (CNH3), a cross-coupling capacitive structure C(I2), a cross-coupling capacitive structure C(PH4), and a cross-coupling capacitive structure C(NH4). The cross-coupling capacitive structure C(PH3), the cross-coupling capacitive structure (CNH3), the cross-coupling capacitive structure C(I2), the cross-coupling capacitive structure C(PH4), and the cross-coupling capacitive structure C(NH4) are also embodiments of the cross-coupling capacitive structures C described above with regard to FIG. 21.

As shown in FIG. 26, the cross-coupling capacitive structure C(PH3) and the cross-coupling capacitive structure C(NH3) are arranged to form a third capacitive voltage divider. The third capacitive voltage divider is electrically connected to the resonator R(1,1). More specifically, the cross-coupling capacitive structure C(PH3) is electrically connected between the end 217 of the inductor 208 and a common connection node H3. The cross-coupling capacitive structure C(NH3) is electrically connected between the end 218 of the inductor 208 and the common connection node H3. Additionally, the cross-coupling capacitive structure C(PH4) and the cross-coupling capacitive structure C(NH4) are arranged to form a fourth capacitive voltage divider. The fourth capacitive voltage divider is electrically connected to the resonator R(1,2). More specifically, the cross-coupling capacitive structure C(PH4) is electrically connected between the end 220 of the inductor 212 and a common connection node H4. The cross-coupling capacitive structure C(NH4) is electrically connected between the end 222 of the inductor 212 and the common connection node H4. As shown in FIG. 26, the cross-coupling capacitive structure C(I2) is electrically connected between first capacitive voltage divider and the second capacitive voltage divider. More specifically, the cross-coupling capacitive structure C(I2) is electrically connected between the common connection node H3 and the common connection node H4. Alternatively, the cross-coupling capacitive structure C(I1) and the cross-coupling capacitive structure C(I2) can be replaced with shorts. The arrangement of the cross-coupling capacitive structure C(PH1), the cross-coupling capacitive structure C(NH1), the cross-coupling capacitive structure C(PH2), the cross-coupling capacitive structure C(NH2), the cross-coupling capacitive structure C(I1), the cross-coupling capacitive structure C(PH3), the cross-coupling capacitive structure C(NH3), the cross-coupling capacitive structure C(PH4), the cross-coupling capacitive structure C(NH4), and the cross-coupling capacitive structure C(I2) shown in FIG. 26 is a double H-bridge structure.

With regard to the third capacitive voltage divider, the cross-coupling capacitive structure C(PH3) is a variable cross-coupling capacitive structure configured to vary a third variable positive electric coupling coefficient provided between the resonator R(1,1) and the common connection node H3. The cross-coupling capacitive structure C(NH3) is a variable cross-coupling capacitive structure configured to vary a third variable negative electric coupling coefficient provided between the resonator R(1,1) and the common connection node H3. Thus, a mutual electric coupling coefficient of the resonator R(1,1) is approximately equal to the first variable positive electric coupling coefficient, the third variable positive electric coupling coefficient, the first variable negative electric coupling coefficient and the third variable negative electric coupling coefficient.

With regard to the fourth capacitive voltage divider, the cross-coupling capacitive structure C(PH4) is a variable cross-coupling capacitive structure configured to vary a fourth variable positive electric coupling coefficient provided between the resonator R(1,2) and the common connection node H4. The cross-coupling capacitive structure C(NH4) is a variable cross-coupling capacitive structure configured to vary a fourth variable negative electric coupling coefficient provided between the resonator R(1,2) and the common connection node H4. Thus, a mutual electric coupling coefficient of the resonator R(1,2) is approximately equal to the second variable positive electric coupling coefficient, the fourth variable positive coupling coefficient, the second variable negative coupling coefficient, and the fourth variable negative electric coupling coefficient. Furthermore, the cross-coupling capacitive structure C(I2) is a variable cross-coupling capacitive structure configured to vary a second variable intermediate electric coupling coefficient provided between the common connection node H3 and the common connection node H4. The first tunable RF filter path 66 shown in FIG. 26 thus has a total mutual coupling coefficient between the resonator R(1,1) and the resonator R(1,2) equal to the sum total of the mutual magnetic coupling coefficient between the inductor 208 and the inductor 212, the mutual electric coupling coefficient of the resonator R(1,1), the mutual electric coupling coefficient of the resonator R(1,2), the first variable intermediate electric coupling coefficient provided between the common connection node H1 and the common connection node H2 and the second variable intermediate electric coupling coefficient provided between the common connection node H3 and the common connection node H4. The double H-bridge structure thus includes two H-bridge structures. The two H-bridge structures allow for common-mode signal transfers of the two H-bridge structures to oppose one another and thereby be reduced and even cancelled.

FIG. 27 illustrates still another exemplary embodiment of the first tunable RF filter path 66 in the first RF filter structure 60 shown in FIG. 21. While the exemplary embodiment shown in FIG. 27 is of the first tunable RF filter path 66, any of the tunable RF filter paths shown in the first RF filter structure 60 of FIG. 21 may be arranged in accordance with the exemplary embodiment shown in FIG. 27. The first tunable RF filter path 66 shown in FIG. 27 includes the same embodiment of the resonator R(1,1) and the same embodiment of the resonator R(1,2) described above with respect to FIG. 22. In addition, the first tunable RF filter path 66 shown in FIG. 27 includes the cross-coupling capacitive structure C(P1) and the cross-coupling capacitive structure (CN1) that form the V-bridge structure described above with respect to FIG. 22. However, the first tunable RF filter path 66 shown in FIG. 27 further includes a resonator R(1,3) and a resonator R(1,4). More specifically, the resonator R(1,3) includes an inductor 226, a capacitive structure 228, and a capacitive structure 230. The resonator R(1,4) includes an inductor 232 and a capacitive structure 234.

With regard to the resonator R(1,3), the inductor 226 is electrically connected between the capacitive structure 228 and the capacitive structure 230. More specifically, the inductor 226 has an end 236 and an end 238, which are disposed opposite to one another. The end 236 is electrically connected to the capacitive structure 228 and the end 238 is electrically connected to the capacitive structure 230. Both the capacitive structure 228 and the capacitive structure 230 are grounded. Thus, the resonator R(1,3) is a differential resonator. In this embodiment, each of the capacitive structure 228 and the capacitive structure 230 is a variable capacitive structure.

With regard to the resonator R(1,4), the inductor 232 and the capacitive structure 234 are electrically connected in parallel. More specifically, the inductor 232 has an end 240 and an end 242, which are disposed opposite to one another. The ends 240, 242 are each electrically connected to the capacitive structure 234, which is grounded. Thus, the resonator R(1,4) is a single-ended resonator.

In this embodiment, the resonator R(1,1), the resonator R(1,2), the resonator R(1,3), and the resonator R(1,4) are all weakly coupled to one another. The resonator R(1,3) and the resonator R(1,4) are weakly coupled by providing the inductor 226 and the inductor 232 such that the inductor 226 and the inductor 232 are weakly coupled. The resonators R(1,1), R(1,2), R(1,3), and R(1,4) are each operably associated with one another such that energy transfer factors between the resonators R(1,1), R(1,2), R(1,3), and R(1,4) are less than 10%. Although the resonator R(1,3) and the resonator R(1,4) are weakly coupled, the inductor 232 has a maximum lateral width and a displacement between the inductor 226 and the inductor 232 is less than or equal to half the maximum lateral width of the inductor 232. As such, the inductor 226 and the inductor 232 are relatively close to one another. The displacement between the inductor 226 and the inductor 232 may be measured from a geometric centroid of the inductor 226 to a geometric centroid of the inductor 232. The maximum lateral width may be a maximum dimension of the inductor 232 along a plane defined by its largest winding. The weak coupling between the inductor 226 and the inductor 232 is obtained through topological techniques. For example, the inductor 226 and the inductor 232 may be fully or partially aligned, where winding(s) of the inductor 226 and winding(s) of the inductor 232 are configured to provide weak coupling through cancellation. Alternatively or additionally, a plane defining an orientation of the windings of the inductor 226 and a plane defining an orientation of the windings of the inductor 232 may be fully or partially orthogonal to one another.

In some embodiments, all of the inductors 208, 212, 226, 232 are provided such that displacements between each of the inductors 208, 212, 226, 232 are less than or equal to half the maximum lateral width of the inductor 212. Alternatively, in other embodiments, only a proper subset of the inductors 208, 212, 226, 232 has displacements that are less than or equal to half the maximum lateral width of the inductor 212. For example, while the displacement between the inductor 208 and the inductor 212 may be less than or equal to half the maximum lateral width of the inductor 212 and the displacement between the inductor 226 and the inductor 232 may be less than or equal to half the maximum lateral width of the inductor 232, the displacements from the inductor 208 and the inductor 212 to the inductor 226 and the inductor 232 may each be greater than half the maximum lateral width of the inductor 212 and half the maximum lateral width of the inductor 232.

The inductors 208, 212, 226, and 232 are magnetically coupled to the each other such that an RF signal received at the end 217 of the inductor 208 with a voltage polarity (i.e., either a positive voltage polarity or a negative voltage polarity) results in filtered RF signals with the same voltage polarity being transmitted out the end 220 of the inductor 212, the end 236 of the inductor 226, and the end 240 of the inductor 232. Also, the inductors 208, 212, 226, and 232 are magnetically coupled to the each other such that an RF signal received at the end 240 of the inductor 232 with a voltage polarity (i.e., either a positive voltage polarity or a negative voltage polarity) results in filtered RF signals with the same voltage polarity being transmitted out the end 217 of the inductor 208, the end 220 of the inductor 212, and the end 236 of the inductor 226. This is indicated in FIG. 27 by the dot convention where a dot is placed at the end 217 of the inductor 208, a dot is placed at the end 220 of the inductor 212, a dot is placed at the end 236 of the inductor 226, and a dot is placed at the end 240 of the inductor 232.

The first tunable RF filter path 66 shown in FIG. 27 includes a cross-coupling capacitive structure C(P3), a cross-coupling capacitive structure C(N3), a cross-coupling capacitive structure C(P4), and a cross-coupling capacitive structure C(N4) electrically connected between the resonator R(1,2) and the resonator R(1,3). With respect to the resonator R(1,2) and the resonator R(1,3), the cross-coupling capacitive structure C(P3), the cross-coupling capacitive structure C(N3), the cross-coupling capacitive structure C(P4) and the cross-coupling capacitive structure C(N4) are arranged to have the X-bridge structure described above with respect to FIG. 23. Thus, the cross-coupling capacitive structure C(P3) is electrically connected between the end 220 and the end 236 so as to provide a variable positive electric coupling coefficient between the resonator R(1,2) and the resonator R(1,3). The cross-coupling capacitive structure C(P3) is a variable cross-coupling capacitive structure configured to vary the variable positive electric coupling coefficient provided between the resonator R(1,2) and the resonator R(1,3). Also, the cross-coupling capacitive structure C(N3) is electrically connected between the end 220 and the end 238 so as to provide a variable negative electric coupling coefficient between the resonator R(1,2) and the resonator R(1,3). The cross-coupling capacitive structure C(N3) is a variable cross-coupling capacitive structure configured to vary the variable negative electric coupling coefficient provided between the resonator R(1,2) and the resonator R(1,3).

Additionally, the cross-coupling capacitive structure C(P4) is electrically connected between the end 222 and the end 238 so as to provide another variable positive electric coupling coefficient between the resonator R(1,2) and the resonator R(1,3). The cross-coupling capacitive structure C(P4) is a variable cross-coupling capacitive structure configured to vary the other variable positive electric coupling coefficient provided between the resonator R(1,2) and the resonator R(1,3). Finally, the cross-coupling capacitive structure C(N4) is electrically connected between the end 222 and the end 236 so as to provide another variable negative electric coupling coefficient between the resonator R(1,2) and the resonator R(1,3). The cross-coupling capacitive structure C(N4) is a variable cross-coupling capacitive structure configured to vary the other variable negative electric coupling coefficient provided between the resonator R(1,2) and the resonator R(1,3).

With respect to the resonator R(1,3) and the resonator R(1,4), the first tunable RF filter path 66 shown in FIG. 27 includes a cross-coupling capacitive structure C(P5) and a cross-coupling capacitive structure C(N5) electrically connected between the resonator R(1,3) and the resonator R(1,4). With respect to the resonator R(1,3) and the resonator R(1,4), the cross-coupling capacitive structure C(P5) and the cross-coupling capacitive structure C(N5) are arranged to have the V-bridge structure described above with respect to FIG. 22. Thus, the cross-coupling capacitive structure C(P5) is electrically connected between the end 236 and the end 240 so as to provide a variable positive electric coupling coefficient between the resonator R(1,3) and the resonator R(1,4). The cross-coupling capacitive structure C(P5) is a variable cross-coupling capacitive structure configured to vary the variable positive electric coupling coefficient provided between the resonator R(1,3) and the resonator R(1,4). Also, the cross-coupling capacitive structure C(N5) is electrically connected between the end 238 and the end 240 so as to provide a variable negative electric coupling coefficient between the resonator R(1,3) and the resonator R(1,4). The cross-coupling capacitive structure C(N5) is a variable cross-coupling capacitive structure configured to vary the variable negative electric coupling coefficient provided between the resonator R(1,3) and the resonator R(1,4).

The embodiment of first RF filter structure 60 shown in FIG. 27 also includes a cross-coupling capacitive structure C(P6), a cross-coupling capacitive structure C(N6), a cross-coupling capacitive structure C(P7), a cross-coupling capacitive structure C(N7), and a cross-coupling capacitive structure C(P8). With respect to the resonator R(1,1) and the resonator R(1,3), the cross-coupling capacitive structure C(P6) and the cross-coupling capacitive structure C(N6) are each electrically connected between the resonator R(1,1) and the resonator R(1,3). The cross-coupling capacitive structure C(P6) is electrically connected between the end 217 and the end 236 so as to provide a variable positive electric coupling coefficient between the resonator R(1,1) and the resonator R(1,3). The cross-coupling capacitive structure C(P6) is a variable cross-coupling capacitive structure configured to vary the variable positive electric coupling coefficient provided between the resonator R(1,1) and the resonator R(1,3). Also, the cross-coupling capacitive structure C(N6) is electrically connected between the end 217 and the end 238 so as to provide a variable negative electric coupling coefficient between the resonator R(1,1) and the resonator R(1,3). The cross-coupling capacitive structure C(N6) is a variable cross-coupling capacitive structure configured to vary the variable negative electric coupling coefficient provided between the resonator R(1,1) and the resonator R(1,3).

With respect to the resonator R(1,2) and the resonator R(1,4), the cross-coupling capacitive structure C(P7) and the cross-coupling capacitive structure C(N7) are each electrically connected between the resonator R(1,2) and the resonator R(1,4). The cross-coupling capacitive structure C(P7) is electrically connected between the end 220 and the end 240 so as to provide a variable positive electric coupling coefficient between the resonator R(1,2) and the resonator R(1,4). The cross-coupling capacitive structure C(P7) is a variable cross-coupling capacitive structure configured to vary the variable positive electric coupling coefficient provided between the resonator R(1,2) and the resonator R(1,4). Also, the cross-coupling capacitive structure C(N7) is electrically connected between the end 222 and the end 240 so as to provide a variable negative electric coupling coefficient between the resonator R(1,2) and the resonator R(1,4). The cross-coupling capacitive structure C(N7) is a variable cross-coupling capacitive structure configured to vary the variable negative electric coupling coefficient provided between the resonator R(1,2) and the resonator R(1,4).

With respect to the resonator R(1,1) and the resonator R(1,4), the cross-coupling capacitive structure C(P8) is electrically connected between the resonator R(1,1) and the resonator R(1,4). The cross-coupling capacitive structure C(P8) is electrically connected between the end 217 and the end 240 so as to provide a variable positive electric coupling coefficient between the resonator R(1,1) and the resonator R(1,4). The cross-coupling capacitive structure C(P8) is a variable cross-coupling capacitive structure configured to vary the variable positive electric coupling coefficient provided between the resonator R(1,1) and the resonator R(1,4).

Furthermore, in this embodiment, a variable capacitive structure 244 is electrically connected in series between the terminal 200 and the resonator R(1,1). The variable capacitive structure 244 is configured to vary a variable impedance of the first tunable RF filter path 66 as measured into the terminal 200 in order to match a source or a load impedance at the terminal 200. In addition, a variable capacitive structure 245 is electrically connected in series between the resonator R(1,4) and the terminal 202. The variable capacitive structure 245 is configured to vary a variable impedance of the first tunable RF filter path 66 as seen into the terminal 202 in order to match a source or a load impedance at the terminal 202.

FIGS. 28A through 28D illustrate different embodiments of the first RF filter structure 60, wherein each of the embodiments has different combinations of input terminals and output terminals. The first RF filter structure 60 can have various topologies. For example, the embodiment of the first RF filter structure 60 shown in FIG. 28A has a single input terminal IN and an integer number i of output terminals OUT1-OUTi. As will be discussed below, the first RF filter structure 60 may define various tunable RF filter paths (e.g., the first tunable RF filter path 66, the second tunable RF filter path 68, the third tunable RF filter path 110, the fourth tunable RF filter path 112, the fifth tunable RF filter path 122, and the sixth tunable RF filter path 124 shown in FIGS. 4, 8, 11, 12, and 14-20) that may be used to receive different RF signals at the input terminal IN and transmit a different filtered RF signal from each of the output terminals OUT1-OUTi. As such, the first RF filter structure 60 shown in FIG. 28A may be specifically configured to provide Single Input Multiple Output (SIMO) operations.

With regard to the embodiment of the first RF filter structure 60 shown in FIG. 28B, the first RF filter structure 60 has an integer number j of input terminals IN1-INj and a single output terminal OUT. As will be discussed below, the first RF filter structure 60 may define various tunable RF filter paths (e.g., the first tunable RF filter path 66, the second tunable RF filter path 68, the third tunable RF filter path 110, the fourth tunable RF filter path 112, the fifth tunable RF filter path 122, and the sixth tunable RF filter path 124 shown in FIGS. 4, 8, 11, 12, and 14-20) that may be used to receive a different RF signal at each of the input terminals IN1-INj and transmit different filtered RF signals from the single output terminal OUT. As such, the first RF filter structure 60 shown in FIG. 28B may be specifically configured to provide Multiple Input Single Output (MISO) operations.

With regard to the embodiment of the first RF filter structure 60 shown in FIG. 28C, the first RF filter structure 60 has a single input terminal IN and a single output terminal OUT. As will be discussed below, the first RF filter structure 60 may define various tunable RF filter paths (e.g., the first tunable RF filter path 66, the second tunable RF filter path 68, the third tunable RF filter path 110, the fourth tunable RF filter path 112, the fifth tunable RF filter path 122, and the sixth tunable RF filter path 124 shown in FIGS. 4, 8, 11, 12, and 14-20) that may be used to receive different RF signals at the single input terminal IN and transmit different filtered RF signals from the output terminal OUT. As such, the first RF filter structure 60 shown in FIG. 28A may be specifically configured to provide Single Input Single Output (SISO) operations.

With regard to the embodiment of the first RF filter structure 60 shown in FIG. 28D, the first RF filter structure 60 has the input terminals IN1-INj and the output terminals OUT1-OUTi. As will be discussed below, the first RF filter structure 60 may define various tunable RF filter paths (e.g., the first tunable RF filter path 66, the second tunable RF filter path 68, the third tunable RF filter path 110, the fourth tunable RF filter path 112, the fifth tunable RF filter path 122, and the sixth tunable RF filter path 124 shown in FIGS. 4, 8, 11, 12, and 14-20) that may be used to receive a different RF signal at each of the input terminal IN1-INj and transmit a different filtered RF signal from each of the output terminals OUT1-OUTi.

FIG. 29 illustrates another embodiment of the first RF filter structure 60. The first RF filter structure 60 shown in FIG. 29 includes one embodiment of the first tunable RF filter path 66 and one embodiment of the second tunable RF filter path 68. The first tunable RF filter path 66 includes the resonator R(1,1) and the resonator R(1,2). The resonator R(1,1) and the resonator R(1,2) are thus a first pair of weakly coupled resonators in the first tunable RF filter path 66. The second tunable RF filter path 68 includes the resonator R(2,1) and the resonator R(2,2). The resonator R(2,1) and the resonator R(2,2) are thus a second pair of weakly coupled resonators in the second tunable RF filter path 68.

As explained in further detail below, a set S of cross-coupling capacitive structures is electrically connected between the resonator R(1,1), the resonator R(1,2), the resonator R(2,1), and the resonator R(2,2) in the first tunable RF filter path 66 and the second tunable RF filter path 68. More specifically, the set S includes a cross-coupling capacitive structure C(PM1), a cross-coupling capacitive structure C(PM2), a cross-coupling capacitive structure C(PM3), a cross-coupling capacitive structure C(PM4), a cross-coupling capacitive structure C(NM1), and a cross-coupling capacitive structure C(NM2). The set S of cross-coupling capacitive structures interconnects the resonator R(1,1), the resonator R(1,2), the resonator R(2,1), and the resonator R(2,2) so that the first RF filter structure 60 shown in FIG. 29 is a matrix (in this embodiment, a 2×2 matrix) of the resonators R. In alternative embodiments, some of the cross-coupling capacitive structures C(PM1), C(PM2), C(PM3), C(PM4), C(NM1), and C(NM2) may be omitted depending on the filter transfer function to be provided.

Unlike in the embodiment of the first RF filter structure 60 shown in FIG. 21, in this embodiment, the first tunable RF filter path 66 and the second tunable RF filter path 68 are not independent of one another. The set S of cross-coupling capacitive structures thus provides for additional tunable RF filter paths to be formed from the resonator R(1,1), the resonator R(1,2), the resonator R(2,1), and the resonator R(2,2). As discussed in further detail below, the arrangement of the first RF filter structure 60 shown in FIG. 29 can be used to realize examples of each of the embodiments of the first RF filter structure 60 shown in FIGS. 28A-28D.

The cross-coupling capacitive structure C(PM1) is electrically connected within the first tunable RF filter path 66, while the cross-coupling capacitive structure C(PM4) is electrically connected within the second tunable RF filter path 68. More specifically, the cross-coupling capacitive structure C(PM1) is electrically connected between the resonator R(1,1) and the resonator R(1,2) in the first tunable RF filter path 66. The cross-coupling capacitive structure C(PM1) is a variable cross-coupling capacitive structure configured to provide and vary a (e.g., positive or negative) electric coupling coefficient between the resonator R(1,1) and the resonator R(1,2). The cross-coupling capacitive structure C(PM4) is a variable cross-coupling capacitive structure configured to provide and vary a (e.g., positive or negative) electric coupling coefficient between the resonator R(2,1) and the resonator R(2,2) in the second tunable RF filter path 68.

To provide additional tunable RF filter paths, the cross-coupling capacitive structure C(PM2), the cross-coupling capacitive structure C(PM3), the cross-coupling capacitive structure C(NM1), and the cross-coupling capacitive structure C(NM2) are each electrically connected between the first tunable RF filter path 66 and the second tunable RF filter path 68. The cross-coupling capacitive structure C(PM2) is a variable cross-coupling capacitive structure configured to provide and vary a (e.g., positive or negative) electric coupling coefficient between the resonator R(1,2) and the resonator R(2,2). The cross-coupling capacitive structure C(PM3) is a variable cross-coupling capacitive structure configured to provide and vary a (e.g., positive or negative) electric coupling coefficient between the resonator R(1,1) and the resonator R(2,1). The cross-coupling capacitive structure C(NM1) is a variable cross-coupling capacitive structure configured to provide and vary a (e.g., positive or negative) electric coupling coefficient between the resonator R(1,1) and the resonator R(2,2). The cross-coupling capacitive structure C(NM2) is a variable cross-coupling capacitive structure configured to provide and vary a (e.g., positive or negative) electric coupling coefficient between the resonator R(1,2) and the resonator R(2,1).

The first tunable RF filter path 66 is electrically connected between the input terminal IN1 and the output terminal OUT1. In addition, the second tunable RF filter path 68 is electrically connected between an input terminal IN2 and an output terminal OUT2. Accordingly, the first RF filter structure 60 shown in FIG. 29 is an embodiment of the first RF filter structure 60 shown in FIG. 28D. However, the input terminal IN2 and the output terminal OUT1 are optional and may be excluded in other embodiments. For example, if the input terminal IN2 were not provided, but the output terminal OUT1 and the output terminal OUT2 were provided, the first RF filter structure 60 shown in FIG. 29 would be provided as an embodiment of the first RF filter structure 60 shown in FIG. 28A. It might, for example, provide a diplexing or a duplexing function. Furthermore, more than two input terminals or output terminals can be provided. Some examples include embodiments of the first RF filter structure 60 used for triplexing, quadplexing, herplexing, and providing FDD and carrier aggregation.

The first tunable RF filter path 66 still provides a path between the input terminal IN1 and the output terminal OUT1. However, assuming that the input terminal IN2 is not provided for SIMO operation, the cross-coupling capacitive structure C(NM1) is electrically connected between the first tunable RF filter path 66 and the second tunable RF filter path 68 to define a first additional tunable RF filter path between the input terminal IN1 and the output terminal OUT2. The first additional tunable RF filter path is thus provided by a portion of the first tunable RF filter path 66 and a portion of the second tunable RF filter path 68. More specifically, the first additional tunable RF filter path includes the resonator R(1,1) and the resonator R(2,2). The first additional tunable RF filter path also includes the cross-coupling capacitive structure C(NM1) that is electrically connected between the resonator R(1,1) and the resonator R(1,2). A second additional tunable RF filter path, a third additional tunable RF filter path, a fourth additional tunable RF filter path, and a fifth additional tunable RF filter path are also defined from the input terminal IN1 to the output terminal OUT2. The second additional tunable RF filter path includes the resonator R(1,1), the cross-coupling capacitive structure C(PM1), the resonator R(1,2), the cross-coupling capacitive C(PM2), and the resonator R(2,2). Additionally, the third additional tunable RF filter path includes the resonator R(1,1), the cross-coupling capacitive structure C(PM3), the resonator R(2,1), the cross-coupling capacitive C(PM4), and the resonator R(2,2). The fourth additional tunable RF filter path includes the resonator R(1,1), the cross-coupling capacitive structure C(PM1), the resonator R(1,2), the cross-coupling capacitive C(NM2), the resonator R(2,1), the cross-coupling capacitive structure C(PM4), and the resonator R(2,2). Finally, the fifth additional tunable RF filter path includes the resonator R(1,1), the cross-coupling capacitive structure C(PM3), the resonator R(2,1), the cross-coupling capacitive C(NM2), the resonator R(1,2), the cross-coupling capacitive structure C(PM2), and the resonator R(2,2).

If the output terminal OUT1 were not provided, but the input terminal IN1 and the input terminal IN2 were provided, the first RF filter structure 60 shown in FIG. 29 would be provided as an embodiment of the first RF filter structure 60 shown in FIG. 28B. In this case, the second tunable RF filter path 68 still provides a path between the input terminal IN2 and the output terminal OUT2. However, assuming that the output terminal OUT1 is not provided for MISO operation, the first additional tunable RF filter path, the second additional tunable RF filter path, the third additional tunable RF filter path, the fourth additional tunable RF filter path, and the fifth additional tunable RF filter path would provide the paths from the input terminal IN1 to the output terminal OUT2.

Finally, if the input terminal IN2 and the output terminal OUT2 were not provided, the first RF filter structure 60 shown in FIG. 29 would be provided as an embodiment of the first RF filter structure 60 shown in FIG. 28C. In this case, the second tunable RF filter path 68 still provides a path between the input terminal IN2 and the output terminal OUT2. However, assuming that the output terminal IN1 is not provided for MISO operation, the first additional tunable RF filter path, the second additional tunable RF filter path, the third additional tunable RF filter path, the fourth additional tunable RF filter path, and the fifth additional tunable RF filter path would provide the paths from the input terminal IN1 to the output terminal OUT2. This may constitute a SISO filter implemented with an array to allow for a large number of signal paths and thus create one or more notches in the transfer function.

With regard to the resonators R(1,1), R(1,2), R(2,1), R(2,2) shown in FIG. 29, the resonators R(1,1), R(1,2), R(2,1), R(2,2) may each be single-ended resonators, differential resonators, or different combinations of single-ended resonators and differential resonators. The resonator R(1,1) and the resonator R(1,2) in the first tunable RF filter path 66 may each be provided in accordance with any of the embodiments of the resonator R(1,1) and the resonator R(1,2) described above with respect to FIGS. 22-27. For example, the resonator R(1,1) may include the inductor 208 (see FIG. 24) and the capacitive structure 210 (see FIG. 24). The resonator R(1,2) may include the inductor 212 and the capacitive structure 214 (see FIG. 24). The resonator R(2,1) may include an inductor (like the inductor 208 in FIG. 24) and a capacitive structure (like the capacitive structure 210 shown in FIG. 24). The resonator R(2,2) may include an inductor (like the inductor 212 in FIG. 24) and a capacitive structure (like the capacitive structure 214 shown in FIG. 24).

Additionally, one or more of the resonators R(1,1), R(1,2) in the first tunable RF filter path 66 and one or more of the resonators R(2,1), R(2,2) in the second tunable RF filter path 68 may be weakly coupled. Thus, the resonators R(1,1), R(1,2), R(2,1), R(2,2) may be operably associated with one another such that an energy transfer factor between each of the resonators R(1,1), R(1,2), R(2,1), R(2,2) is less than 10%. Alternatively, the energy transfer factor between only a subset of the resonators R(1,1), R(1,2), R(2,1), R(2,2) is less than 10%. In addition, in at least some embodiments, not all of the resonators R(1,1), R(1,2), R(2,1), R(2,2) are weakly coupled to one another.

In this embodiment, the inductor 208 (see FIG. 24) of the resonator R(1,1), the inductor 212 (see FIG. 24) of the resonator R(1,2), the inductor of the resonator R(2,1), and the inductor of the resonator R(2,2) may all be weakly coupled to one another. In some embodiments, displacements between the inductor 208 (see FIG. 24) of the resonator R(1,1), the inductor 212 (see FIG. 24) of the resonator R(1,2), the inductor of the resonator R(2,1), and the inductor of the resonator R(2,2) may all be less than or equal to half the maximum lateral width of the inductor 212. Alternatively, in other embodiments, only a proper subset of the inductor 208 (see FIG. 24) of the resonator R(1,1), the inductor 212 (see FIG. 24) of the resonator R(1,2), the inductor of the resonator R(2,1), and the inductor of the resonator R(2,2) may have displacements that are less than or equal to half the maximum lateral width of the inductor 212.

FIG. 30 illustrates yet another embodiment of the first RF filter structure 60. The first RF filter structure 60 includes the resonators R described above with respect to FIG. 21. The resonators R of the first RF filter structure 60 shown in FIG. 30 are arranged as a two-dimensional matrix of the resonators R. In this embodiment, the first RF filter structure 60 includes an embodiment of the first tunable RF filter path 66, an embodiment of the second tunable RF filter path 68, an embodiment of the third tunable RF filter path 110, and an embodiment of the fourth tunable RF filter path 112. Thus, the integer M for the first RF filter structure 60 shown in FIG. 30 is four (4) or greater. Additionally, the integer N for the first RF filter structure 60 shown in FIG. 30 is 3 or greater. Note that in alternative embodiments, the integer M may be two (2) or greater and the integer N may be two(2) or greater. It should be noted that in alternative embodiments the number of resonators R in each row and column may be the same or different.

In the embodiment of the first RF filter structure 60 shown in FIG. 30, the first tunable RF filter path 66 includes the resonator R(1,1), the resonator R(1,2), and one or more additional resonators R, such as the resonator R(1,N), since the integer N is 3 or greater. All of the weakly coupled resonators R(1,1) through R(1,N) are weakly coupled to one another. Furthermore, the first tunable RF filter path 66 is electrically connected between a terminal TU1 and a terminal TANT1. With regard to the second tunable RF filter path 68, the second tunable RF filter path 68 includes the resonator R(2,1), the resonator R(2,2), and one or more additional resonators R, such as the resonator R(2,N), since the integer N is 3 or greater. All of the weakly coupled resonators R(2,1) through R(2,N) are weakly coupled to one another. Furthermore, the second tunable RF filter path 68 is electrically connected between a terminal TU2 and a terminal TANT2.

With regard to the third tunable RF filter path 110, the third tunable RF filter path 110 includes a resonator R(3,1), a resonator R(3,2), and one or more additional resonators R, such as a resonator R(3,N), since the integer N is 3 or greater. All of the weakly coupled resonators R(3,1) through R(3,N) are weakly coupled to one another. Alternatively, only a proper subset of them may be weakly coupled to one another. Furthermore, the third tunable RF filter path 110 is electrically connected between a terminal TU3 and a terminal TANT3. With regard to the fourth tunable RF filter path 112, the fourth tunable RF filter path 112 includes the resonator R(M,1), the resonator R(M,2), and one or more additional resonators R, such as the resonator R(M,N), since the integer N is 3 or greater. All of the weakly coupled resonators R(M,1) through R(M,N) are weakly coupled to one another. Alternatively, only a proper subset of them may be weakly coupled to one another. Furthermore, the fourth tunable RF filter path 112 is electrically connected between a terminal TU4 and a terminal TANT4.

The first tunable RF filter path 66 is configured to receive RF signals and output filtered RF signals. It should be noted that the first RF filter structure 60 may include any number of tunable RF filter paths, such as, for example, the third tunable RF filter path 110, the fourth tunable RF filter path 112, the fifth tunable RF filter path 122, and the sixth tunable RF filter path 124, described above with respect to FIGS. 11-14. Each of the resonators R may be a tunable resonator, which allows for a resonant frequency of each of the resonators to be varied to along a frequency range. In alternative embodiments, only a proper subset of the resonators R may be tunable. In still another embodiment, all of the resonators R are not tunable, but rather have a fixed transfer function.

In some embodiments, all of the resonators R in the first RF filter structure 60 shown in FIG. 30 are weakly coupled to one another. Thus, the resonators R may all be operably associated with one another such that energy transfer factors between the resonators R are less than 10%. Alternatively, the energy transfer factor is less than 10% only among a proper subset of the resonators R. In other embodiments, only the resonators R in adjacent tunable RF filter paths 66, 68, 110, 112 are weakly coupled to one another. For example, all the resonators R(1,1) through R(1,N) may be weakly coupled to all the resonators R(2,1) through R(2,N). In still other embodiments, only subsets of adjacent resonators R may be weakly coupled to each other. For example, the resonators R(1,1), R(1,2) may be weakly coupled to the resonators R(2,1), R(2,2), while the resonators R(3,1), R(3,2) may be weakly coupled to the resonators R(M,1), R(M,2). These and other combinations would be apparent to one of ordinary skill in the art in light of this disclosure.

Sets S(1), S(2), S(3), S(4), S(5), and S(6) of cross-coupled capacitive structures are electrically connected between the resonators R. Each of the sets S(1), S(2), S(3), S(4), S(5), and S(6) is arranged like the set S of cross-coupled capacitive structures described above with respect to FIG. 29. For example, in one particular exemplary embodiment (e.g., when M=4 and N=3), the set S(1) of cross-coupled capacitive structures is electrically connected between the resonators R(1,1), R(1,2) in the first tunable RF filter path 66 and the resonators R(2,1), R(2,2) in the second tunable RF filter path 68. The set S(2) of cross-coupled capacitive structures is electrically connected between the resonators R(1,2), R(1,N) in the first tunable RF filter path 66 and the resonators R(2,2), R(2,N) in the second tunable RF filter path 68. The set S(3) of cross-coupled capacitive structures is electrically connected between the resonators R(2,1), R(2,2) in the second tunable RF filter path 68 and the resonators R(3,1), R(3,2) in the third tunable RF filter path 110. The set S(4) of cross-coupled capacitive structures is electrically connected between the resonators R(2,2), R(2,N) in the second tunable RF filter path 68 and the resonators R(3,2), R(3,N) in the third tunable RF filter path 110. The set S(5) of cross-coupled capacitive structures is electrically connected between the resonators R(3,1), R(3,2) in the third tunable RF filter path 110 and the resonators R(M,1), R(M,2) in the fourth tunable RF filter path 112. Finally, the set S(6) of cross-coupled capacitive structures is electrically connected between the resonators R(3,2), R(3,N) in the third tunable RF filter path 110 and the resonators R(M,2), R(M,N) in the fourth tunable RF filter path 112. Note that some cross-coupled capacitive structures in the sets S(1), S(2), S(3), S(4), S(5), and S(6) of cross-coupled capacitive structures for the resonators R in adjacent columns or in adjacent ones of the tunable RF filter paths 66, 68, 110, 112 overlap. This is because in the matrix of the resonators R, each of the resonators R is adjacent to multiple other ones of the resonators R. In another embodiment, the sets S(1), S(2), S(3), S(4), S(5), and S(6) of cross-coupled capacitive structures may be connected between non-adjacent resonators R. For example, there may be cross-coupled capacitive structures between resonators R that are more than one column or row apart.

FIG. 31 illustrates the embodiment of the first RF filter structure 60 shown in FIG. 30 electrically connected to the first RF antenna 16, the second RF antenna 32, a third RF antenna 246, and a fourth RF antenna 247. More specifically, the first tunable RF filter path 66 is electrically connected to the first RF antenna 16 at the terminal TANT1. The second tunable RF filter path 68 is electrically connected to the second RF antenna 32 at the terminal TANT2. The third tunable RF filter path 110 is electrically connected to the third RF antenna 246 at the terminal TANT3. The fourth tunable RF filter path 112 is electrically connected to the fourth RF antenna 247 at the terminal TANT4. With the sets S(1), S(2), S(3), S(4), S(5), and S(6) of cross-coupled capacitive structures, the first RF filter structure 60 shown in FIG. 31 forms an interconnected two-dimensional matrix of the resonators R. Thus, in addition to the first tunable RF filter path 66, the second tunable RF filter path 68, the third tunable RF filter path 110, and the fourth tunable RF filter path 112, the sets S(1), S(2), S(3), S(4), S(5), and S(6) of cross-coupled capacitive structures provide a multitude of additional tunable RF filter paths between the terminals TU1, TU2, TU3, TU4 and the terminals TANT1, TANT2, TANT3, TANT4. It should be noted that in alternative embodiments, the terminals TANT1, TANT2, TANT3, TANT4 may not be connected to antennas. Some antennas may be omitted depending on the functionality being realized.

By tuning the sets S(1), S(2), S(3), S(4), S(5), and S(6), the first RF filter structure 60 shown in FIG. 31 can be tuned so that any combination of the resonators R is selectable for the propagation of RF signals. More specifically, the first RF filter structure 60 shown in FIG. 31 is tunable to route RF receive signals from any combination of the terminals TANT1, TANT2, TANT3, TANT4 to any combination of the terminals TU1, TU2, TU3, TU4. Additionally, the first RF filter structure 60 shown in FIG. 31 is tunable to route RF transmission signals from any combination of the terminals TU1, TU2, TU3, TU4 to the terminals TANT1, TANT2, TANT3, TANT4. Accordingly, the first RF filter structure 60 can be configured to implement various MIMO, SIMO, MISO, and SISO operations.

FIG. 32 illustrates the first RF filter structure 60 shown in FIGS. 30 and 31 with examples of additional tunable RF filter paths 248, 250 highlighted. It should be noted, however, that there are a vast number of additional combinations of the resonators R that may be selected to provide tunable RF filter paths (e.g., the first tunable RF filter path 66, the second tunable RF filter path 68, the third tunable RF filter path 110, the fourth tunable RF filter path 112, the additional tunable RF filter path 248, and the additional tunable RF filter path 250) between the terminals TU1, TU2, TU3, TU4 and the terminals TANT1, TANT2, TANT3, TANT4. An explicit description of all of the various combinations of the resonators R that may be implemented with the first RF filter structure 60 shown in FIGS. 30-32 is simply impractical given the high number of possible combinations. Along with the previous descriptions, the additional tunable RF filter paths 248, 250 are highlighted in FIG. 32 simply to give examples of the basic concepts. However, the combinations provided for the additional tunable RF filter paths 248, 250 are in no way limiting, as any combination of the resonators R may be selected to route RF signals between the terminals TU1, TU2, TU3, TU4 and the terminals TANT1, TANT2, TANT3, TANT4. Any number of functions, such as signal combining, splitting, multiplexing, and demultiplexing, with various filtering profiles for each, may be realized.

With regard to the additional tunable RF filter paths 248, 250 highlighted in FIG. 32, the additional tunable RF filter paths 248, 250 may be used during MIMO, SIMO, MISO, and SISO operations. More specifically, the additional tunable RF filter path 248 connects the terminal TANT1 to the terminal TU2. The additional tunable RF filter path 250 connects the terminal TANT3 to the terminal TU2. As such, the first RF filter structure 60 may be tuned so that the additional tunable RF filter path 248 and the additional tunable RF filter path 250 are selected in a MISO operation from the terminal TANT1 and the terminal TANT3 to the terminal TU2. The additional tunable RF filter paths 248, 250 may also be used in SIMO operations. For example, the first RF filter structure 60 may be tuned so that the first tunable RF filter path 66 and the additional tunable RF filter path 248 are selected in a SIMO operation from the terminal TU2 to the terminal TANT1. The additional tunable RF filter paths 248, 250 can also be used in SISO operations from the terminal TANT1 to the terminal TU2 or from the terminal TANT3 to the terminal TU2. Finally, the additional tunable RF filter paths 248, 250 may also be used in SIMO operations. For instance, the first RF filter structure 60 may be tuned so that the first tunable RF filter path 66 and the additional tunable RF filter path 250 are selected in a SIMO operation from the terminal TANT1 to the terminal TU1 and from the terminal TANT3 to the terminal TU2.

In some applications involving the first RF filter structure 60 in FIGS. 30-32, MISO and SIMO operations can be used in conjunction with wideband antenna cables or fiber for transmitting RF signals in multiple RF communication frequency bands. Specific communication frequency bands can be processed by certain dedicated RF filtering paths in the first RF filter structure 60. For example, different RF signals may be injected from a wideband antenna and then propagated along different dedicated tunable RF filter paths in the first RF filter structure 60 to the terminals TU1, TU2, TU3, TU4. These dedicated tunable RF filter paths can be configured to have a transfer function that is specifically designed to handle these RF signals. Furthermore, the first RF filter structure 60 shown in FIGS. 30-32 is configured to tune a transfer function of any of the specific tunable RF filter paths (e.g., the first tunable RF filter path 66, the second tunable RF filter path 68, the third tunable RF filter path 110, the fourth tunable RF filter path 112, the additional tunable RF filter path 248, and the additional tunable RF filter path 250) in the first RF filter structure 60 by tuning resonators R that are not in the specific tunable RF filter path being used to route RF signals. This can help reduce out-of-band noise and reduce insertion losses. It can also improve isolation and out-of-band attenuation.

FIG. 33 illustrates yet another embodiment of the first RF filter structure 60. The first RF filter structure 60 includes the resonators R and is arranged as a two-dimensional matrix of the resonators R, where N is equal to four (4) and M is equal to three (3). In this embodiment, the first RF filter structure 60 includes an embodiment of the first tunable RF filter path 66, an embodiment of the second tunable RF filter path 68, and an embodiment of the third tunable RF filter path 110. It should be noted that in alternative embodiments, the number of resonators R in each row and column may be the same or different.

In the embodiment of the first RF filter structure 60 shown in FIG. 33, the first tunable RF filter path 66 includes the resonator R(1,1), the resonator R(1,2), the resonator R(1,3), and the resonator R(1,4). Furthermore, the first tunable RF filter path 66 is electrically connected between the terminal TU1 and the terminal TANT1. With regard to the second tunable RF filter path 68, the second tunable RF filter path 68 includes the resonator R(2,1), the resonator R(2,2), a resonator R(2,3), and a resonator R(2,4). Furthermore, the second tunable RF filter path 68 is electrically connected between the terminal TU2 and the terminal TANT2. With regard to the third tunable RF filter path 110, the third tunable RF filter path 110 includes the resonator R(3,1), the resonator R(3,2), a resonator R(3,3), and a resonator R(3,4). Furthermore, the third tunable RF filter path 110 is electrically connected between the terminal TU3 and the terminal TANT3.

In this embodiment, the resonators R in a subset 252 of the resonators R(1,1), R(1,2) in the first tunable RF filter path 66 are weakly coupled to one another. A cross-coupling capacitive structure CS1 is electrically connected between the resonators R(1,1), R(1,2). The cross-coupling capacitive structure CS1 is a variable cross-coupling capacitive structure configured to vary a variable electric coupling coefficient between the resonators R(1,1), R(1,2). A subset 254 of the resonators R(1,3), and R(1,4) in the second tunable RF filter path 68 is also weakly coupled to each other. A cross-coupling capacitive structure CS2 is electrically connected between the resonators R(1,3), R(1,4). The cross-coupling capacitive structure CS2 is a variable cross-coupling capacitive structure configured to vary a variable electric coupling coefficient between the resonators R(1,3), R(1,4).

As shown in FIG. 33, a unidirectional coupling stage 256 is electrically connected within the first tunable RF filter path 66. The unidirectional coupling stage 256 defines an amplifier gain and is configured to provide amplification within the first tunable RF filter path 66 in accordance with the amplifier gain. In some embodiments, the amplifier gain of the unidirectional coupling stage 256 is a variable amplifier gain. In this embodiment, the unidirectional coupling stage 256 is electrically connected between the resonator R(1,2) and the resonator R(1,3). The variable amplifier gain can thus control a variable electric coupling coefficient between the resonator R(1,2) in the subset 252 and the resonator R(1,3) in the subset 254. Since the unidirectional coupling stage 256 is an active semiconductor component, the unidirectional coupling stage 256 is unidirectional and thus only allows signal propagations from an input terminal IA of the unidirectional coupling stage 256 to an output terminal OA of the unidirectional coupling stage 256. Thus, the resonator R(1,2) in the subset 252 is unidirectionally mutual electrically coupled to the resonator R(1,3) in the subset 254.

Note that the resonators R(1,3), R(1,4) in the subset 254 are not electrically connected to the second tunable RF filter path 68 and the third tunable RF filter path 110. As such, the unidirectional coupling stage 256 thus results in a portion of the first tunable RF filter path 66 with the subset 254 of the resonators R(1,3), R(1,4) to be unidirectional. Consequently, signal flow can be to the terminal TANT1 but not from the terminal TANT1. Since the unidirectional coupling stage 256 is unidirectional, the variable amplifier gain (and thus the variable electric coupling coefficient between the resonator R(1,2) and the resonator R(1,3)) may be controlled using feed-forward control techniques and/or feedback control techniques.

Next, the resonators R in a subset 258 of the resonators R(2,1), R(2,2), R(3,1), and R(3,2) in the second tunable RF filter path 68 and in the third tunable RF filter path 110 are weakly coupled to one another. An unidirectional coupling stage 260 is electrically connected between the first tunable RF filter path 66 and the second tunable RF filter path 68. More specifically, the unidirectional coupling stage 260 is electrically connected between the resonator R(1,1) and the resonator R(2,1). The unidirectional coupling stage 260 defines an amplifier gain and is configured to provide amplification in accordance with the amplifier gain. In some embodiments, the amplifier gain of the unidirectional coupling stage 260 is a variable amplifier gain. The variable amplifier gain thus can control a variable electric coupling coefficient between the resonator R(1,1) in the subset 252 and the resonator R(2,1) in the subset 258. A cross-coupling capacitive structure CS3 is electrically connected between the resonator R(1,2) and the resonator R(2,2). The cross-coupling capacitive structure CS3 is a variable cross-coupling capacitive structure configured to vary a variable electric coupling coefficient between the resonators R(1,2), R(2,2).

To interconnect the resonators R(2,1), R(2,2), R(3,1), and R(3,2), a set S(A) of cross-coupling capacitive structures is electrically connected between the resonators R(2,1), R(2,2), R(3,1), and R(3,2) in the subset 258. The set S(A) of cross-coupling capacitive structures is arranged like the set S of cross-coupling capacitive structures described above with respect to FIG. 29. Additionally, the resonators R in a subset 262 of the resonators R(2,3), R(2,4), R(3,3), and R(3,4) in the second tunable RF filter path 68 and in the third tunable RF filter path 110 are weakly coupled to one another. A set S(B) of cross-coupling capacitive structures is electrically connected between the resonators R(2,3), R(2,4), R(3,3), and R(3,4) in the subset 262. The set S(B) of cross-coupling capacitive structures is arranged like the set S of cross-coupling capacitive structures described above with respect to FIG. 29.

To interconnect the subset 258 and the subset 262, the first RF filter structure 60 shown in FIG. 33 includes a cross-coupling capacitive structure CS4 and a unidirectional coupling stage 264. The cross-coupling capacitive structure CS4 is electrically connected between the resonators R(2,2), R(2,3). The cross-coupling capacitive structure CS4 is a variable cross-coupling capacitive structure configured to vary a variable electric coupling coefficient between the resonators R(2,2), R(2,3). The unidirectional coupling stage 264 is electrically connected within the third tunable RF filter path 110. In this embodiment, the unidirectional coupling stage 264 is electrically connected between the resonator R(3,3) and the resonator R(3,2). The unidirectional coupling stage 264 defines an amplifier gain and is configured to provide amplification within the third tunable RF filter path 110 in accordance with the amplifier gain. In some embodiments, the amplifier gain of the unidirectional coupling stage 264 is a variable amplifier gain. The variable amplifier gain can thus control a variable electric coupling coefficient between the resonator R(3,3) in the subset 262 and the resonator R(3,2) in the subset 258. Since the unidirectional coupling stage 264 is an active semiconductor component, the unidirectional coupling stage 264 is unidirectional and thus only allows signal propagations from an input terminal IB of the unidirectional coupling stage 264 to an output terminal OB of the unidirectional coupling stage 264. Thus, the resonator R(3,3) in the subset 262 is unidirectionally mutual electrically coupled to the resonator R(3,2) in the subset 258. Consequently, the third tunable RF filter path 110 shown in FIG. 33 is unidirectional if the signal flow is between the terminal TANT3 and the terminal TU3 though the third tunable RF filter path 110. As such signal flow between the terminal TANT3 and the terminal TU3 is provided only through the third tunable RF filter path 110, signal flow can only be from the terminal TANT3 to the terminal TU3, and not vice versa. In other cases, an additional tunable RF signal path (e.g., the additional RF terminal tunable RF signal path that includes the resonators R(3,1), R(2,2), R(2,3) and R(3,4)) can be tuned to provide bidirectional signal flow between the terminal TU3 and the terminal TANT3 through the cross-coupling capacitive structure CS4. The unidirectional coupling stages 256, 260, 264 may be active devices, such as amplifiers, diodes, transistors, networks of transistors, buffer stages, attenuation stages, and the like. The unidirectional coupling stages 256, 260, 264 can have gains higher than one (1), lower than one (1), or equal to one (1). Additionally, the unidirectional coupling stages 256, 260, 264 may be passive devices. The unidirectional coupling stages 256, 260, 264 may not be entirely or ideally unilateral, but may have some finite reverse coupling. In this case, the unidirectional coupling stages 256, 260, 264 may be predominately unilateral. One example in which the unidirectional coupling stages 256, 260, 264 may be used for multi-resonator applications and may improve isolation between certain parts, such as transmission ports and receive ports of a duplexer.

FIG. 34 illustrates yet another embodiment of the first RF filter structure 60. The first RF filter structure 60 shown in FIG. 34 is integrated into an IC package 266. The first RF filter structure 60 shown in FIG. 34 includes the resonators R and is arranged as a two-dimensional matrix of the resonators R, where N is equal to three (3) and M is equal to two (2). It should be noted that in alternative embodiments the number of resonators R in each row and column may be the same or different.

In this embodiment, the first RF filter structure 60 includes an embodiment of the first tunable RF filter path 66 and an embodiment of the second tunable RF filter path 68. The first tunable RF filter path 66 includes the resonator R(1,1), the resonator R(1,2), and the resonator R(1,3). The second tunable RF filter path 68 includes the resonator R(2,1), the resonator R(2,2), and the resonator R(2,3). A set S(X) of cross-coupling capacitive structures is electrically connected between the resonators R(1,1), R(1,2), R(2,1), and R(2,2). The set S(X) of cross-coupling capacitive structures is arranged like the set S of cross-coupling capacitive structures described above with respect to FIG. 29. A set S(Y) of cross-coupling capacitive structures is electrically connected between the resonators R(1,2), R(1,3), R(2,2), and R(2,3). The set S(Y) of cross-coupling capacitive structures is also arranged like the set S of cross-coupling capacitive structures described above with respect to FIG. 29.

As shown in FIG. 34, the IC package 266 houses a package substrate 268, a semiconductor die 270, and a semiconductor die 272. The semiconductor die 270 and the semiconductor die 272 are mounted on the package substrate 268. In this embodiment, the resonators R of the first RF filter structure 60 are formed by the package substrate 268. The set S(X) of cross-coupling capacitive structures is formed by the semiconductor die 270. On the other hand, the set S(Y) of cross-coupling capacitive structures is formed by the semiconductor die 272. Thus, the set S(X) of cross-coupling capacitive structures and the set S(Y) of cross-coupling capacitive structures are formed on multiple and separate semiconductor dies 270, 272. Using the multiple and separate semiconductor dies 270, 272 may be helpful in order to increase isolation. The multiple and separate semiconductor dies 270, 272 may have less area than the semiconductor die 268 shown in FIG. 34. As such, the embodiment shown in FIG. 35 may consume less die area.

FIG. 35 illustrates another embodiment of an IC package 266′ that houses the same embodiment of the first RF filter structure 60 described above with regard to FIG. 34. The IC package 266′ is the same as the IC package 266 shown in FIG. 34, except that the IC package 266′ only has a single semiconductor die 274. In this embodiment, both the set S(X) of cross-coupling capacitive structures and the set S(Y) of cross-coupling capacitive structures are formed by the semiconductor die 272. Thus, the IC package 266′ allows for a more compact arrangement than the IC package 266.

FIG. 36 illustrates yet another embodiment of the first RF filter structure 60. In this embodiment, the first RF filter structure 60 is arranged as a three-dimensional matrix of resonators R1, R2, R3. More specifically, a two-dimensional matrix of the resonators R1 is provided on a plane k, a two-dimensional array of the resonators R2 is provided on a plane m, and a two-dimensional array of the resonators R3 is provided on a plane n. Cross-coupling capacitive structures CC are electrically connected between the resonators R1, R2, R3 that are adjacent to one another in the same plane k,m,n and in the different planes k,m,n. The three-dimensional matrix of resonators R1, R2, R3 thus allows for more resonators to be cross-coupled to one another. This allows for the first RF filter structure 60 to provide greater numbers of tunable RF filter paths and allows for the first RF filter structure 60 to be tuned more accurately.

In general, having more tunable RF filter paths allows for the synthesis of a more complex transfer function with multiple notches for better blocker rejection. The number of resonators R1, R2, R3 in each of the planes k, n, m may be different or the same. The three-dimensional matrix of resonators can be used in MIMO, SIMO, MISO, and SISO applications.

With regard to each of the embodiments of the first RF filter structure 60 described with respect to the Figures above, the components provided in the first RF filter structure 60 may be formed precisely as designed since the first RF filter structure 60 can be formed through an IC process that allows for manufacturing variations within certain error tolerances. These manufacturing variations thus may result in the components in the first RF filter structure 60 to be formed with some manufacturing error. Furthermore, the components of the first RF filter structure 60 may suffer from environmental variations, such as temperature variations, supply voltage variations, operating power variations, and/or the like. In order to maintain the Q factor of the first RF filter structure 60 as high as possible, the first RF filter structure 60 should be calibrated so as to compensate for manufacturing variations and environmental variations.

FIG. 37 illustrates an embodiment of the RF front-end circuitry 58 with the first RF filter structure 60. The first RF filter structure 60 may be provided as any one of the embodiments of the first RF filter structure 60 described with respect to the Figures above. Accordingly, the first RF filter structure 60 described above may be used in duplexing, diplexing, multiplexing, carrier aggregation, MIMO, SIMO, MISO, and SISO applications, as described above. Also, the RF front-end circuitry 58 may be provided in accordance to any one of the embodiments of the RF front-end circuitry 58 described above. However, in this embodiment, the RF front-end control circuitry 98 provided in the RF front-end circuitry 58 includes a calibration circuit 300 that calibrates the first RF filter structure 60. The calibration circuit 300 is configured to provide calibration during the calibration mode.

As mentioned above, the first RF filter structure 60 shown in FIG. 37 may be provided in accordance with any of the embodiments described above. Nevertheless, to help explain the concepts relate to the calibration circuit 300 and for the sake of clarity, the first RF filter structure 60 is presumed to be provided in accordance with the embodiment shown in FIG. 30. Thus, the first RF filter structure 60 includes the terminals TU1, TU2, TU3, TU4 and the terminals TANT1, TANT2, TANT3, TANT4. In addition, the first RF filter structure includes the first tunable RF filter path 66, the second tunable RF filter path 68, the third tunable RF filter path 110 and the fourth tunable RF filter path 112 as shown in FIG. 30.

The terminals TU1, TU2, TU3, TU4 are connected to RF circuitry (e.g., the RF receive circuitry 62 and/or the RF transmit circuitry 64) within the RF front-end circuitry 58. The terminals TANT1, TANT2, TANT3, TANT4 are connected to one or more of the antennas 16, 32, 246, 247. For example, as described in the embodiment shown in FIG. 11, the terminals TANT1, TANT2, TANT3, TANT4 may be connected to the first RF antenna 16 at the first common connection node 74. On the other hand, each of the terminals TANT1, TANT2, TANT3, TANT4 may be connected to a different one of the antennas 16, 32, 246, 247, as described above with respect to FIG. 31. Any other combination of connections between the terminals TANT1, TANT2, TANT3, TANT4 and the antennas 16, 32, 246, 247 may also be provided. In alternative applications, any other devices capable of conveying communication signals may be connected to the terminals TANT1, TANT2, TANT3, TANT4 such as cables, fiber optics, and/or the like.

The first RF filter structure 60 defines a transfer function. The first RF filter structure 60 is tunable so that the transfer function defines one or more passbands. More specifically, the first RF filter structure 60 can be tuned to provide one or more passbands between any of the terminals TU1, TU2, TU3, TU4, and any of the terminals TANT1, TANT2, TANT3, TANT4. In this manner, RF signals can be routed between the terminals TU1, TU2, TU3, TU4, and the terminals TANT1, TANT2, TANT3, TANT4, while at the same time filtering is provided. For example, the first tunable RF filter path 66 is tunable so that the transfer function defines a passband between the terminal TU1 and the terminal TANT1. The second tunable RF filter path 68 is tunable so that the transfer function defines a passband between the terminal TU2 and the terminal TANT2. The third tunable RF filter path 110 is tunable so that the transfer function defines a passband between the terminal TU3 and the terminal TANT3. The fourth tunable RF filter path 112 is tunable so that the transfer function defines a passband between the terminal TU4 and the terminal TANT4. Other transfer shapes may also be defined by the transfer function besides the passbands.

The same is true for any combination of the terminals TU1, TU2, TU3, TU4, and the terminals TANT1, TANT2, TANT3, TANT4. More specifically, as described above with respect to FIGS. 30 and 32, there are a vast number of combinations of the resonators R (shown in FIG. 32) that may be selected to provide tunable RF filter paths (e.g., the first tunable RF filter path 66, the second tunable RF filter path 68, the third tunable RF filter path 110, the fourth tunable RF filter path 112, the additional tunable RF filter path 248 (shown in FIG. 32), and the additional tunable RF filter path 250 (shown in FIG. 32)) between the terminals TU1, TU2, TU3, TU4 and the terminals TANT1, TANT2, TANT3, TANT4. For example, the additional tunable RF filter path 248 (shown in FIG. 32) is tunable to define a passband between the terminal TU2 and the terminal TANT1. The additional tunable RF filter path 250 (shown in FIG. 32) is tunable to define a passband between the terminal TU2 and the terminal TANT3.

However, manufacturing variations can cause the components in the first RF filter structure 60 to cause errors in the transfer function. For example, manufacturing errors can result in parasitic coupling within capacitive structures of the first RF filter structure 60 and/or for undesired variations in reactances. Aging of components also shifts the performance of the first RF filter structure 60 as time passes. In addition, environmental variations can cause inductors and capacitive structures in the first RF filter structure 60 to not operate as designed. Finally, note that the RF front-end control circuitry 98 is configured to tune the first RF filter structure 60 so that the passbands are transposed into different RF communication bands. The effects of manufacturing variations and environmental variations are generally frequency-dependent, and thus undesired variations of the components in the first RF filter structure 60 may change non-linearly depending on which RF communication band a particular passband is transposed into. Aging is a very slow varying process in most applications but is still dynamic. Environmental variations are also slow and dynamic. They can be compensated for by using one or multiple calibrations (e.g., calibrations in between signal bursts or during down time). Manufacturing variations are static for a given design and may be corrected once at production or during start-up of the RF front end circuitry 58. Accordingly, the calibration circuit 300 is provided to calibrate the first RF filter structure 60 in order to compensate for manufacturing variations and/or environmental variations in one or more RF communications bands. Calibration of the first RF filter structure 60 may be performed by the calibration circuit 300 upon fabrication and/or during operation (e.g., power up, between communication bursts, each time the passband(s) are transposed into a different RF communication band, etc.).

For each of the passbands that can be defined by the transfer function between the terminals TU1, TU2, TU3, TU4 and the terminals TANT1, TANT2, TANT3, TANT4, the calibration circuit 300 is configured to shape the passband so that the passband defines a center frequency. Thus, for example, the first RF filter structure 60 may be tuned to transpose the passband into a particular RF communication band. However, as a result of manufacturing variations, the passband may have excessive ripple so as not to adequately define the center frequency. Thus, once the passband has been transposed into the particular RF communication band, the calibration circuit 300 is configured to shape the passband so as to adequately define the center frequency and desired filtering shape. For instance, magnitude detection or a replica resonator may be used to shape the passband, as explained in further detail below. The center frequency of the passband is generally placed near a target center frequency. However, calibration techniques employing magnitude detection and the replica resonator are generally limited in accuracy. This is because an amplitude response of the transfer function is relatively flat near the center frequency, thereby making it difficult to precisely detect a frequency displacement between the center frequency of the passband and the target center frequency once the center frequency is near the target center frequency.

Accordingly, for each of the passbands that can be defined by the transfer function between the terminals TU1, TU2, TU3, TU4 and the terminals TANT1, TANT2, TANT3, TANT4, the calibration circuit 300 is configured to detect a phase difference between (at least one of) a pair of weakly coupled resonators R (shown in FIG. 30) at the target center frequency. Since a phase response of the transfer function is steep at the center frequency of the passband, detecting the frequency displacement can be done much more accurately with the phase difference. As such, the calibration circuit 300 is configured to adjust the phase difference of (at least) the pair of weakly coupled resonators at the target center frequency so as to reduce the frequency displacement between the center frequency of the passband and the target center frequency. Furthermore, as explained in further detail below, for each of the passbands that can be defined by the transfer function between the terminals TU1, TU2, TU3, TU4 and the terminals TANT1, TANT2, TANT3, TANT4, the calibration circuit 300 may be configured to create a notch adjacent to the passband and thus increase out-of-band rejection. Additionally, the calibration circuit 300 may be configured to detect phase differences for two or more tunable RF filter paths, e.g. the first tunable RF filter path 66, the second tunable RF filter path 68, the third tunable RF filter path 110, the fourth tunable RF filter path 112, the additional tunable RF filter path 248 (shown in FIG. 32), and the additional tunable RF filter path 250 (shown in FIG. 32)) at target notch frequencies (or some other related frequencies) and adjust coupling coefficients and/or resonator capacitances to create a notch at the target notch frequency, as explained in further detail below.

As described above with respect to FIGS. 30 and 32, there are a vast number of combinations of the resonators R (shown in FIG. 32) that may be selected to provide tunable RF filter paths (e.g., the first tunable RF filter path 66, the second tunable RF filter path 68, the third tunable RF filter path 110, the fourth tunable RF filter path 112, the additional tunable RF filter path 248 (shown in FIG. 32), and the additional tunable RF filter path 250 (shown in FIG. 32)) between the terminals TU1, TU2, TU3, TU4 and the terminals TANT1, TANT2, TANT3, TANT4. In one embodiment, the calibration circuit 300 is configured to detect the phase difference between any combination of the resonators R. In another embodiment, the calibration circuit 300 is configured to detect the phase difference of the resonators R that are adjacent to one another. Alternative embodiments of the calibration circuit 300 may be configured to detect the phase difference of any combination of the resonators, which may depend on an RF application for the first RF filter structure 300, cost-considerations, and RF requirements.

The RF front-end circuitry 58 described in FIG. 37 may be provided in accordance to any of the other embodiments of the RF front-end circuitry 58 described above. However, in one example, the terminals TU1, TU2, TU3, TU4 are connected to the RF receive circuit 64 and the RF transmit circuitry 62 in accordance with the embodiment described above with respect to FIG. 11. Thus, the terminal TU1 is connected to the first connection node 70 and the RF transmit circuitry 64. The terminal TU2 is connected to the second connection node 72 and the RF transmit circuitry 64. The terminal TU3 is connected to the third connection node 114 and the RF receive circuitry 62. Furthermore, the terminal TU4 is connected to the fourth connection node 116 and the RF receive circuitry 62. Accordingly, in this case, the terminal TU1 and the terminal TU2 are input terminals of the first RF filter structure 60 while the terminal TANT1 and the terminal TANT2 are output terminals of the first RF filter structure 60. The terminal TANT3 and the terminal TANT4 are input terminals of the first RF filter structure 60 while the terminal TU3 and the terminal TU4 are output terminals of the first RF filter structure 60. Thus, in this case, the passband of the transfer function provided by the first tunable RF filter path 66 is thus defined from the terminal TANT1 to the terminal TU1. The passband of the transfer function provided by the second tunable RF filter path 68 is thus defined from the terminal TANT2 to the terminal TU2. The passband of the transfer function provided by the third tunable RF filter path 110 is thus defined from the terminal TU3 to the terminal TANT3. Finally, the passband of the transfer function provided by the fourth tunable RF filter path 112 is thus defined from the terminal TU4 to the terminal TANT4.

In order to detect the phase differences between the resonators R (shown in FIG. 32) of the first RF filter structure 60, the calibration circuit 300 is configured to receive a feedback input 302 from the first RF filter structure 60. The calibration circuit 300 may use the feedback input 302 to detect magnitudes of the transfer response at the resonators R. For example, the feedback input 302 may include one or more feedback signals from each of the resonators R in the first RF filter structure 60. Alternatively, the feedback input 302 may include one or more feedback signal from only a proper subset of the resonators R. In one embodiment, the feedback signals are the calibration status signals CSS1 to CSSQ described above with respect to FIG. 13.

To calibrate the transfer response of the first RF filter structure 60, the calibration circuit 300 is configured to generate an impedance control output 304 based on the feedback input 302. The impedance control output 304 is generated by the calibration circuit 300 and may include one or more impedance control signals that dynamically adjust the variable capacitances of the cross-coupling capacitive structures and the capacitive structures within the resonators R (shown in FIG. 32) to provide calibration. For example, the impedance control output 304 may include the calibration control signal CCS1 to CCSN described above with respect to FIG. 13. Additionally or alternatively, the impedance control output 304 may include subsets of digital impedance control signals that indicate different digital words that set the variable capacitances within the first RF filter structure 60.

Referring now to FIGS. 37 and 38, FIG. 38 illustrates one embodiment of transfer response of the first RF filter structure 60 that has been tuned to define a passband 310 within an RF communication band 312 prior to calibration by the calibration circuit 300. In particular, FIG. 38 illustrates a frequency response curve 314, which is an amplitude response of the transfer function. The passband 310 may be defined by the transfer function of the first RF filter structure 60 between any one of the terminals TU1, TU2, TU3, TU4 and any one of the terminals TANT1, TANT2, TANT3, TANT4. For example, the passband 310 may be defined by the transfer function after the first RF filter structure 60 has been tuned by the RF front-end control circuitry 98 so that the passband 310 is transposed within the RF communication band 312. The RF communication band 312 may be an RF transmit frequency band or an RF receive frequency band, depending on the application.

Note that, prior to calibration, the passband 310 may not adequately define a center frequency but rather is degraded due to undesired process variations and/or environmental variations of the components in the first RF filter structure 60. More specifically, the passband 310 defines a low passband edge frequency f_(L) and a high passband edge frequency f_(H). The low passband edge frequency f_(L) and the high passband edge frequency f_(H) are relatively spread out. Thus, a Q factor of the passband 310 is a low ratio of a center frequency to bandwidth. Furthermore, the passband 310 has ripples at frequencies f₁, f₂, through f_(n) and does not adequately define the center frequency. Finally, while the passband 310 has been transposed within the RF communication band 312, the passband 310 is not aligned with a target center frequency f_(TC) with the RF communication band 312. These defects are the result of the resonators R (shown in FIG. 30) and the cross-coupling capacitive structures in the tunable RF filter path (e.g., the first tunable RF filter path 66, the second tunable RF filter path 68, the third tunable RF filter path 110, the fourth tunable RF filter path 112, the additional tunable RF filter path 248, and the additional tunable RF filter path 250 shown in FIG. 32) that provide the passband 310 are not set appropriately. During the calibration mode, the calibration circuit 300 is configured to calibrate the passband 310 and compensate for the effects of undesired process variations and/or environmental variations.

Referring now to FIGS. 37 and 39, FIG. 39 illustrates one embodiment of the frequency response curve 314 of the first RF filter structure 60 shown in FIG. 37 after the calibration circuit 300 has centered the passband 310 approximately at the target center frequency f_(TC). As shown by FIG. 39, the calibration circuit 300 is configured to shape the passband 310 so that the passband 310 defines a center frequency f_(C) during the calibration mode. The center frequency f_(C) of the passband 310 is a frequency of the passband 310 with a peak magnitude. Any technique may be utilized to shape the passband 310 so that the passband 310 defines the center frequency f_(C) during the calibration mode. As explained in further detail below, magnitude detection or a replica resonator are calibration techniques which may be utilized to shape the passband 310. The center frequency f_(C) of the passband is generally placed near the target center frequency f_(TC) by these techniques. However, calibration techniques employing magnitude detection and the replica resonator are generally limited in accuracy. This is because the frequency response curve 314 (i.e., the amplitude response of the transfer function) is relatively flat near the center frequency f_(C), thereby making it difficult to precisely detect a frequency displacement between the center frequency f_(C) of the passband 310 and the target center frequency f_(TC) once the center frequency f_(C) is near the target center frequency f_(TC).

To provide the center frequency f_(C) closer to the target center frequency f_(TC), the calibration circuit 300 is configured to detect a phase difference at the target center frequency f_(TC) between (at least a pair of) the resonators R (shown in FIG. 32) in the tunable RF filter path (e.g., the first tunable RF filter path 66, the second tunable RF filter path 68, the third tunable RF filter path 110, the fourth tunable RF filter path 112, the additional tunable RF filter path 248, and the additional tunable RF filter path 250 shown in FIG. 32) tuned to define the passband 310 within the RF communication band 312. While the passband 310 is being calibrated by the calibration circuit 300, the calibration circuit 300 may be configured to detect a phase difference at the target center frequency f_(TC) between a pair of the weakly coupled resonators R in the tunable RF filter path (e.g., the first tunable RF filter path 66, the second tunable RF filter path 68, the third tunable RF filter path 110, the fourth tunable RF filter path 112, the additional tunable RF filter path 248, and the additional tunable RF filter path 250 shown in FIG. 32) defining the passband 310. Additionally or alternatively, the calibration circuit 300 may be configured to detect a phase difference at the target center frequency f_(TC) between each combination of the resonators R in the tunable RF filter path (e.g., the first tunable RF filter path 66, the second tunable RF filter path 68, the third tunable RF filter path 110, the fourth tunable RF filter path 112, the additional tunable RF filter path 248, and the additional tunable RF filter path 250 shown in FIG. 32) that has been tuned to define the passband 310. Additionally or alternatively, the calibration circuit 300 may be configured to detect a phase difference at the target center frequency f_(TC) between the adjacent resonators R in the tunable RF filter path (e.g., the first tunable RF filter path 66, the second tunable RF filter path 68, the third tunable RF filter path 110, the fourth tunable RF filter path 112, the additional tunable RF filter path 248, and the additional tunable RF filter path 250 shown in FIG. 32) that has been tuned to define the passband 310. These and other combinations are possible, depending on the application.

The calibration circuit 300 is configured to adjust the phase difference between (at least one pair of) the resonators R at the target center frequency f_(TC) so as to reduce the frequency displacement between the center frequency f_(C) of the passband 310 and the target center frequency f_(TC). For example, while the passband 310 is being calibrated by the calibration circuit 300, the calibration circuit 300 may be configured to adjust the phase difference at the target center frequency f_(TC) between a pair of the weakly coupled resonators R in the tunable RF filter path (e.g., the first tunable RF filter path 66, the second tunable RF filter path 68, the third tunable RF filter path 110, the fourth tunable RF filter path 112, the additional tunable RF filter path 248, and the additional tunable RF filter path 250 shown in FIG. 32) defining the passband 310. Additionally or alternatively, the calibration circuit 300 may be configured to adjust the phase difference at the target center frequency f_(TC) between each combination of the resonators R in the tunable RF filter path (e.g., the first tunable RF filter path 66, the second tunable RF filter path 68, the third tunable RF filter path 110, the fourth tunable RF filter path 112, the additional tunable RF filter path 248, and the additional tunable RF filter path 250 shown in FIG. 32). Additionally or alternatively, the calibration circuit 300 may be configured to adjust the phase difference at the target center frequency f_(TC) between the adjacent resonators R in the tunable RF filter path (e.g., the first tunable RF filter path 66, the second tunable RF filter path 68, the third tunable RF filter path 110, the fourth tunable RF filter path 112, the additional tunable RF filter path 248, and the additional tunable RF filter path 250 shown in FIG. 32) that has been tuned to define the passband 310. These and other combinations are possible, depending on the application.

In this embodiment, the calibration circuit 300 is configured to adjust the phase difference of the resonators R at the target center frequency f_(TC) so as to eliminate the frequency displacement between the center frequency f_(C) of the passband 310 and the target center frequency f_(TC). Thus, as shown in FIG. 39, the center frequency f_(C) and the target center frequency f_(TC) are equal. However, it should be noted that this may or may not be the case. For instance, in other examples, while the frequency displacement may be reduced, the frequency displacement may not be eliminated. In any case, placement accuracy of the center frequency f_(C) is increased because a phase response of the transfer response is steep at the center frequency f_(C). This makes it easier to determine the frequency displacement between the center frequency f_(C) and the target center frequency f_(TC). Furthermore, note that the low passband edge frequency f_(L) and the high passband edge frequency f_(H) are closer, and thus, the Q factor of the passband 310 has been increased.

Referring now to FIG. 37 and FIG. 40, FIG. 40 illustrates one embodiment of the frequency response curve 314 after the calibration circuit 300 has placed a notch 316 in the transfer function adjacent to the passband 310. The notch 316 is provided at a notch frequency f_(NO) and is adjacent to the passband 310 since the notch 316 is defined by roll-off of the passband 310. The calibration circuit 300 is configured to create the notch f_(NO) approximately at a target notch frequency f_(TNO). In this manner, the calibration circuit 300 is configured to calibrate the transfer response to increase out-of-band rejection, particularly there are various communication frequency channels provided near one another within the RF communication band 312. If the transfer function has multiple notches, each of the notches should be calibrated. Any number of notches can be placed on one side or on both sides of the passband.

FIG. 41 illustrates an exemplary embodiment of the first RF filter structure 60 shown in FIG. 37 having a matrix of the resonators R. The first RF filter structure 60 is provided in accordance with the embodiment of the first RF filter structure 60 shown in FIGS. 30-32 above. Again, other embodiments may have any number of the resonators R in any number of rows and columns. Thus, the first RF filter structure 60 also includes the first tunable RF filter path 66, the second tunable RF filter path 68, the third tunable RF filter path 110 (not shown in FIG. 41 for the sake of clarity), and the fourth tunable RF filter path 112 (not shown in FIG. 41 for the sake of clarity). In this embodiment however, match coupling capacitive structures (referred to generically as element 318 and specifically as elements 318(TU1), 318(TANT1), 318(TU2), and 318(TANT2)) are provided in the first RF filter structure 60. More specifically, the first tunable RF filter path 66 includes a match coupling capacitive element 318(TU1) connected between the terminal TU1 and the resonator R(1,1), and a match coupling capacitive element 318(TANT1) is connected between the terminal TANT2 and the resonator R(1,N). The first tunable RF filter path 66 includes a match coupling capacitive element 318(TU1) connected between the terminal TU1 and the resonator R(1,1) and a match coupling capacitive structure 344(TANT1) is connected between the terminal TANT2 and the resonator R(1,N). Other similar match coupling capacitive structures may be provided in the third tunable RF filter path 110 and the fourth tunable RF filter path 112. As explained above with regard to FIG. 30, any combination of the resonators R may be weakly coupled to one another. However, for the sake of clarity and explanation, the resonators R adjacent to one another in the first RF filter structure 60 are weakly coupled to one another. Also, while the matrix of the resonators R may include any number of the resonators R, the integer M is presumed to equal 4 and the integer N is presumed to equal 3, for the sake of explanation.

In this embodiment, the calibration circuit 300 includes a set of detectors 320. More specifically, the calibration is an exemplary embodiment of the calibration circuit 300 with a plurality of amplitude detectors (AM) and a plurality of phase detectors (PM). In this embodiment, the calibration circuit 300 is configured to detect a magnitude of the transfer response from each of the resonators R in the first RF filter structure 60. More specifically, in this embodiment, the set of detectors 320 includes one of the amplitude detectors AM for each of the resonators R. As shown in FIG. 41, the amplitude detectors AM receive a feedback signal 322 from each of the resonators R in order to detect the magnitude of the transfer response from each of the resonators R. In this manner, the calibration circuit 300 is configured to shape the resonators R in the tunable RF filter path of interest so that the passband defines the center frequency near the target center frequency. Magnetic coupling may be provided as an energy coupling mechanism between the resonators R.

For example, after the passband defined by the first tunable RF filter path 66 has been transposed within an RF communication band, the calibration circuit 300 includes an amplitude detector AM that detects a magnitude of the transfer response from the resonator R(1,1) at the center frequency, an amplitude detector AM that detects a magnitude of the transfer response from the resonator R(1,2) at the target center frequency, and an amplitude detector AM that detects a magnitude of the transfer response from the resonator R(1,N) at the target center frequency. The calibration circuit 300 is configured to adjust variable capacitances of the capacitive structures in the resonators R(1,1), R(1,2) and R(1,N) based on the magnitudes of the transfer response from the resonators R(1,1), R(1,2) and R(1,N) so that the center frequency is placed near the target center frequency. The same is true analogously with regard to the other tunable RF filter paths in the first tunable RF filter path 66. In this embodiment, the calibration circuit 300 includes a calibration control device 324 that receives an output from each of the detectors 320 and generates the impedance control output 304 based on the output from each of the detectors.

The impedance control output 304 may itself include several control outputs in order to control the variable capacitances of the capacitive structures in the first RF filter structure 60. In this manner, the calibration control device 324 may adjust the variable capacitances of the capacitive structures within the resonators R(1,1), R(1,2) and R(1,N) in order to provide the center frequency of the passband near the target center frequency. In this case, multi-step calibration of the capacitive structures of the resonators R can also be controlled using phase detectors that measure phase differences.

After shaping the passband so that the center frequency is placed near the target of the target center frequency, the calibration circuit 300 is configured to adjust the phase differences of the resonators R so as to reduce the frequency displacement between the center frequency and the target center frequency. In this embodiment, the calibration circuit 300 includes the phase detectors PM that detect the phase difference between adjacent resonators R in the first RF filter structure 60. Outputs from the phase detectors PM are generated, and the calibration control device 324 generates the impedance control output 304 based on the outputs from the phase detectors PM. In this manner, the phase differences between the adjacent resonators RF are adjusted to reduce the frequency displacement between the center frequency of the passband and the target passband. For example, the calibration circuit 300 is configured to adjust the capacitive values of the capacitive structures in the resonators R(1,1), R(1,2) and R(1,N) to reduce (e.g., eliminate or minimize) the frequency displacement between the center frequency of the passband provided by the first tunable RF filter path 66 and the target center frequency based on the phase differences between the resonators R(1,1), R(1,2) and the resonators R(1,2), R(1,N).

The calibration circuit 300 is also configured to create the notch approximately at the target notch frequency. Different techniques may be utilized to create the notch adjacent to the frequency band. For instance, the cross-coupling capacitive structures in the sets S(1), S(2), S(3) (shown in FIG. 30), and S(4), may be utilized to create the notch. With regard to the passband of the first tunable RF filter path 66, the calibration circuit 300 may vary the variable capacitances of the cross-coupling capacitors in the sets S(1), S(2) to create the notch. Additionally, the calibration circuit 300 may vary the variable capacitances of the match coupling capacitive structure (TU1) and the match coupling capacitive structure C(TANT1) to create the notch adjacent to the passband of the first tunable RF filter path 66.

Note that in this embodiment, a multiplexer 326 is provided which may be connected to the RF receive circuitry 62 (shown in FIG. 37) and the RF transmit circuitry 64 (shown in FIG. 37). An RF tone generator 328 is also connected to the multiplexer. During fabrication, the RF tone generator 328 may be utilized by the calibration circuit 300 to provide an RF tone signal used for calibration. On the other hand, after fabrication, the RF signals to and from the the RF receive circuitry 62 (shown in FIG. 37) and the RF transmit circuitry 64 (shown in FIG. 37) may be used for calibration. The RF tone signal and the RF signals are selected by the calibration circuit 300 using the multiplexer 326.

FIG. 42 illustrates an exemplary arrangement of weakly coupled and adjacent resonators R_(A), R_(B), R_(C) in the first RF filter structure 60 with cross-coupling capacitive structures C_(AB), C_(AC), and C_(BC). The resonators R_(A), R_(B), R_(C) may be any subcombination of the resonators R in the first RF filter structure 60. The coupling capacitive structure C_(AB) is connected between the resonator R_(A) and the resonator R_(B). The coupling capacitive structure C_(AC) is connected between the resonator R_(A) and the resonator R_(C). The coupling capacitive structure is connected between the resonator R_(B) and the resonator R_(C). The resonator R_(A) includes the inductor 208 and the capacitive structure 210. The resonator R_(B) includes the inductor 212 and the capacitive structure 214. The resonator R_(C) includes the inductor 208′ and the capacitive structure 210′. The resonators R_(A) and R_(B) are in the tunable RF filter path 330 (e.g., the first tunable RF filter path 66, the second tunable RF filter path 68, the third tunable RF filter path 110, the fourth tunable RF filter path 112, the additional tunable RF filter path 248, and the additional tunable RF filter path 250 shown in FIG. 32) that has been tuned to define the passband. As explained above with regard to FIG. 41, the capacitive structures 210, 214 are adjusted to center the center frequency at the target center frequency.

FIG. 42 also illustrates an exemplary arrangement of the phase detectors PMAB, PMAC, and PMBC in the calibration circuit 300. The arrangement of the phase detectors PMAB, PMAC, and PMBC in the calibration circuit 300 allows the calibration circuit to adjust the variable capacitances of the cross-coupling capacitors C_(AB), C_(AC), C_(BC) to place the notch adjacent to the passband at the target notch frequency. The phase detector PMAB is configured to receive a feedback signal 332 from the resonator R_(A) and a feedback signal 334 indicating the phase of the resonator R_(B). The phase detector PMAB is configured to detect a phase difference between the resonator R_(A) and the resonator R_(B) by generating a phase detection signal 336 that indicates the phase difference between the resonator R_(A) and the resonator R_(B). The phase detector PMAC is configured to receive the feedback signal 332 and a feedback signal 338 indicating the phase of the resonator R_(C). The phase detector PMAC is configured to detect a phase difference between the resonator R_(A) and the resonator R_(C) by generating a phase detection signal 340 that indicates the phase difference between the resonator R_(A) and the resonator R_(C). The phase detector PMBC is configured to receive the feedback signal 338 and the feedback signal 334. The phase detector PMBC is configured to detect a phase difference between the resonator R_(B) and the resonator R_(C) by generating a phase detection signal 342 that indicates the phase difference between the resonator R_(B) and the resonator R_(C). The feedback signals 332, 338, 334 form part of the feedback input 302. The resonators R_(A), R_(B), R_(C) are weakly coupled by having an energy transfer factor of less than 10%.

The calibration control device 324 of the calibration circuit 300 is configured to generate the impedance control output 304 based on the feedback input 302. More specifically, the calibration circuit 300 is configured to adjust the capacitive structures 210, 214, and 210′ in the resonators R_(A), R_(B), R_(C) to center the passband of the tunable RF filter path 330 at the target center frequency. To create the notch adjacent to the passband, the calibration circuit 300 is configured to adjust the phase difference of the resonators at the target center frequency by being configured to adjust the variable capacitances of the capacitive structure C_(AB), C_(AC), C_(BC) based on the phase detection signals 336, 340, 342.

More specifically, the calibration circuit 300 adjusts the phase difference at the target center frequency between the resonator R_(A) and the resonator R_(C) and the phase difference at the target center frequency between the resonator R_(C) and the resonator R_(B) so that the phase difference at the target center frequency between the resonator R_(A) and the resonator R_(C) and the phase difference at the target center frequency between the resonator R_(C) and the resonator R_(B) is constructive with the phase difference at the target center frequency between resonator R_(A) and the resonator R_(B) in the tunable RF filter path 330. Also, the calibration circuit 300 adjusts the phase difference at the target notch frequency between the resonator R_(A) and the resonator R_(C) and the phase difference at the target notch frequency between the resonator R_(C) and the resonator R_(B) so that the phase difference at the target notch frequency at the target center frequency between the resonator R_(A) and the resonator R_(C) and the phase difference at the target center frequency between the resonator R_(C) and the resonator R_(B) is destructive with the phase difference at the target notch frequency between resonator R_(A) and the resonator R_(B) in the tunable RF filter path 330. The calibration circuit 300 does this by adjusting the variable capacitances of the capacitive structures C_(AB), C_(AC), C_(BC). In this manner, the passband is provided at the target center frequency and the notch is provided approximately at the target notch frequency. At the target center frequency, the phase difference between the resonator R_(A) and the resonator R_(B) should be approximately 90 degrees. To compare the phase differences at a given target notch frequency, an RF tone signal may be injected operating at or close to the target notch frequency. This RF tone signal may be provided externally or generated locally. Alternatively, the phase differences can be measured at different frequencies from the notch (e.g., passband frequencies) if the relative phase shift is known or can be estimated.

After (or simultaneously) the cross-coupling capacitors C_(AB), C_(AC), C_(BC) are adjusted to create the notch adjacent to the passband, the calibration circuit 300 is configured to adjust the variable capacitance of the capacitive structures 210, 214 to compensate for a change to the center frequency of the passband resulting from the variable capacitance of the cross-coupling capacitive structure C_(AB) being adjusted to create the notch adjacent to the passband. For example, if the variable capacitance of the cross-coupling capacitive structure C_(AB) is adjusted by CEX, the capacitive structure 210 is adjusted by (−CEX) and the capacitive structure 210 is adjusted by (CEX). In this manner, an iterative process is not required to provide the center frequency of the passband at the target center frequency while creating the notch adjacent to the passband.

FIG. 43 illustrates an exemplary arrangement of the weakly coupled and adjacent resonators R_(A), R_(B), R_(C) in the first RF filter structure 60 with cross-coupling capacitive structures C_(AB) and C_(AC). In this embodiment, the resonator R_(A) is connected to the match coupling capacitive structure 344 connected between the terminal 346 and the resonator R_(A) in the first RF filter structure 60. FIG. 42 also illustrates and an exemplary arrangement of the phase detectors PMAB, PMAC described above with respect to FIG. 42. In this embodiment, the calibration circuit 300 further comprises the phase detector PMMA. The phase detector PMMA is configured to receive the feedback signal 332 and a feedback signal 348 from the match coupling capacitive structure 344 where the feedback signal 348 indicating the phase of the match coupling capacitive structure 344. The phase detector PMMA is configured to detect a phase difference between the match coupling capacitive structure 344 and the resonator R_(A) by generating a phase detection signal 350 that indicates the phase difference between the match coupling capacitive structure 344 and the resonator R_(A). The phase detector PMMA is configured to detect a phase difference between the match coupling capacitive structure 344 and the resonator R_(A) by generating a phase detection signal 350 that indicates the phase difference between the match coupling capacitive structure and the resonator R_(A). The feedback signals 332, 338, 334, 348 form part of the feedback input 302. The resonators R_(A), R_(B), R_(C) are weakly coupled by having an energy transfer factor of less than 10%.

The calibration control device 324 of the calibration circuit 300 is configured to generate the impedance control output 304 based on the feedback input 302. More specifically, the calibration circuit 300 is configured to adjust the capacitive structures 210, 214, and 210′ in the resonators R_(A), R_(B), R_(C) to center the passband of the tunable RF filter path 330 at the target center frequency, as explained above. To create the notch adjacent to the passband, the calibration circuit 300 is configured to adjust the phase difference of the match coupling capacitive structure 344 and the resonator R_(A) at the target center frequency by being configured to adjust the variable capacitance of the match coupling capacitive structure 344 and the cross coupling capacitive structure C_(AC), based on the phase detection signals 340, 350. More specifically, the calibration circuit 300 adjusts the phase difference at the target center frequency between the match coupling capacitive structure 344 and the resonator R_(A) and the phase difference at the target center frequency between the resonator R_(A) and the resonator R_(C) so that the phase difference at the target center frequency between the match coupling capacitive structure 344 and the resonator is constructive with the phase difference at the target center frequency between resonator R_(A) and the resonator R_(C) in the tunable RF filter path 330. Also, the calibration circuit 300 adjust the phase difference at the target notch frequency between the match coupling capacitive structure 344 and the resonator R_(A) and the phase difference at the target notch frequency between the resonator R_(A) and the resonator R_(C) at the target notch frequency so that the phase difference at the target notch frequency between the match coupling capacitive structure 344 and the resonator R_(A) is destructive with the phase difference at the target notch frequency between resonator R_(A) and the resonator R_(C) in the tunable RF filter path 330. The calibration circuit 300 does this by adjusting the variable capacitance of the match coupling capacitive structure 344 and the cross-coupling capacitive structure C_(AC). In this manner, the passband is provided at the target center frequency and the notch is provided approximately at the target notch frequency.

After the cross-coupling capacitors C_(AB), C_(AC), C_(BC) are adjusted to create the notch adjacent to the passband, the calibration circuit 300 is configured to adjust the variable capacitance of the capacitive structure 210 to compensate for a change to the center frequency of the passband resulting from the variable capacitance of the match coupling capacitive structure 344 being adjusted to create the notch adjacent to the passband. For example, if the variable capacitance of the match coupling capacitive structure 344 is adjusted by CEX, the capacitive structure 210 is adjusted by (−CEX). In this manner, an iterative process is not required to provide the center frequency of the passband at the target center frequency while creating the notch adjacent to the passband.

FIG. 44 illustrates one embodiment of the calibration circuit 300, wherein, in this embodiment, the calibration circuit 300 includes a calibration computational device 352 and a tuning control device 354. The calibration computational device 352 is operably associated with the phase detectors PM and the amplitude detectors AM described above with respect to FIG. 41. The tuning control device 354 is operably associated with the first RF filter structure 60 (shown in FIG. 41) and is configured to generate the impedance control output 304. In this embodiment, the phase detectors PM and the amplitude detectors AM are operably associated with a multiplexer 358. The multiplexer 358 selects an output from the phase detectors PM and the amplitude detectors AM and provides them to an analog to digital converter ADC. The analog to digital converter then provides an output to the calibration computational device 352.

In this embodiment, the calibration computation device 352 includes a calibration computation core 360 that receives the output from the analog to digital converter ADC. The calibration computation core 360 is configured to calculate capacitive values for the variable capacitances in the first RF filter structure 60 (shown in FIG. 41). In addition, a digital interface 362 is operably associated with the calibration computational device 352 to receive other digital parameters, which may indicate the target center frequency, the target notch frequency, operational frequencies, mode settings, and/or the like. The calibration computational device 352 also includes volatile memory and (or) non-volatile memory, which may be used by the calibration computation core to store and retrieve values to determine the capacitive values and/or store the capacitive values. The calibration computation core 360 generates a computational output indicating the capacitive values to the tuning control device 354. The tuning control device 354 then generates the impedance control output 304 to vary the variable capacitances accordingly as described above.

FIG. 45 illustrates one embodiment of a replica resonator RR, which may be provided in the calibration circuit 300 to calibrate the first RF filter structure 60 shown in FIG. 37. In this example, the replica resonator RR is used to shape the passband to have the center frequency placed near the target center frequency. The resonator R includes the inductor 208, which in this embodiment is a folded and 3D inductor, and the capacitive structure 210, which in this embodiment is a metal-insulator-metal (MIM) capacitor. Alternatively or additionally, any combination of metal-on-metal, metal-on-silicon, diode varactor, parasitic layout capacitance, or the like may be used. The replica resonator RR includes an inductor 208(RR) that is intended to operate in proportion with the inductor 208. The replica resonator RR also includes a capacitive structure 210(RR) configured to replicate the capacitive structure 210 in the resonator R. In this case, an inductance of the inductor 208 is determined by the inductance of the metal layers that form the inductor 208. The inductor 208(RR) is not a folded and 3D inductor but is rather a small inductor formed from the same metal layers. As such, inductor 208(RR) mimics the inductance of the inductor 208 but may be significantly smaller. Alternatively, a folded three dimensional inductor can be used for the inductor 208(RR) if substrate area is available and desired. The capacitive structure 210(RR) is identical to the capacitive structure 210.

In addition, a reference oscillator 364 is provided to generate a tone signal 366. The tone signal 366 generates the tone signal 366 at the target center frequency. A frequency measurement device 368 in the calibration circuit 300 is configured to measure an operating RF frequency of the replica resonator RR by counting a number of cycles of the tone signal 366 within a measurement time period after being provided to the replica resonator RR. The frequency measurement device 368 generates a frequency measurement signal 370 that indicates the operating RF frequency of the replica resonator RR. Based on the difference between the operating RF frequency and the target center frequency, the resonator center frequency device 372 is configured to change the variable capacitance of the capacitive structure 210 and the capacitive structure 210(RR) so that the operating RF frequency of the replica resonator RR (and thus the resonator R) are provided at the target center frequency.

Those skilled in the art will recognize improvements and modifications to the preferred embodiments of the present disclosure. All such improvements and modifications are considered within the scope of the concepts disclosed herein and the claims that follow. 

What is claimed is:
 1. A radio frequency (RF) front-end circuitry, comprising: a tunable RF filter structure comprising a pair of weakly coupled resonators, wherein the tunable RF filter structure is tunable to define a transfer function with a passband; a calibration circuit configured to: shape the passband so that the passband defines a center frequency; detect a phase difference between the pair of weakly coupled resonators at a target center frequency; and adjust the phase difference between the pair of weakly coupled resonators at the target center frequency so as to reduce a frequency displacement between the center frequency of the passband and the target center frequency.
 2. The RF front-end circuitry of claim 1 wherein the calibration circuit is further configured to create a notch adjacent to passband.
 3. The RF front-end circuitry of claim 2 wherein: the tunable RF filter structure comprises a first tunable RF filter path that defines the passband of the transfer function, the first tunable RF filter path comprising at least the pair of weakly coupled resonators and a coupling capacitive structure connected to the pair of weakly coupled resonators, the coupling capacitive structure having a variable capacitance; the calibration circuit is configured to create the notch adjacent to the passband by being configured to adjust the variable capacitance of the coupling capacitive structure.
 4. The RF front-end circuitry of claim 3 wherein: the pair of weakly coupled resonators comprises: a first resonator having a first inductor and a first capacitive structure connected to the first inductor, the first capacitive structure having a variable capacitance; and a second resonator having a second inductor and a second capacitive structure connected to the second inductor, wherein the first inductor is weakly coupled to the first inductor and the second capacitive structure has a variable capacitance; the calibration circuit is configured to adjust the phase difference of the pair of weakly coupled resonators at the target center frequency by being configured to adjust the variable capacitance of the first capacitive structure and the variable capacitance of the second capacitive structure.
 5. The RF front-end circuitry of claim 4 wherein the coupling capacitive structure is a cross-coupling capacitive structure connected between the pair of weakly coupled resonators.
 6. The RF front-end circuitry of claim 5 wherein after adjusting the phase difference of the pair of weakly coupled resonators at the target center frequency and adjusting the variable capacitance of the cross-coupling capacitive structure, the calibration circuit is further configured to readjust the variable capacitance of the first capacitive structure and variable capacitance of the second capacitive structure to compensate for a change to the center frequency of the passband resulting from the variable capacitance of the cross-coupling capacitive structure being adjusted to create the notch adjacent to the passband.
 7. The RF front-end circuitry of claim 3 wherein: the tunable RF filter structure includes a first terminal and a second terminal and the first tunable RF filter path connected between the first terminal and the second terminal; and the coupling capacitive structure is connected between the first terminal and a first resonator of the pair of weakly coupled resonators.
 8. The RF front-end circuitry of claim 7 wherein after adjusting the phase difference of the pair of weakly coupled resonators at the target center frequency and adjusting the variable capacitance of the coupling capacitive structure, the calibration circuit is further configured to readjust the variable capacitance of a first capacitive structure to compensate for a change to the center frequency of the passband resulting from the variable capacitance of the coupling capacitive structure being adjusted to create the notch adjacent to the passband.
 9. The RF front-end circuitry of claim 1 wherein: the pair of weakly coupled resonators comprises: a first resonator having a first inductor and a first capacitive structure connected to the first inductor, the first capacitive structure having a variable capacitance; and a second resonator having a second inductor and a second capacitive structure connected to the second inductor, wherein the first inductor is weakly coupled to the first inductor and the second capacitive structure has a variable capacitance; the calibration circuit is configured to shape the passband so that the passband defines the center frequency by being configured to: detect a magnitude of the transfer response from the first resonator around the target center frequency; and detect a magnitude of the transfer response from the second resonator around the target center frequency; adjust a variable capacitance of the first capacitive structure and a variable capacitance of the second capacitive structure based on the magnitude of the transfer response from the first resonator around the center frequency and the magnitude of the transfer response from the second resonator around the target center frequency so that the center frequency is placed near the target center frequency.
 10. The RF front-end circuitry of claim 9 wherein the calibration circuit is configured to adjust the phase difference of the pair of weakly coupled resonators after shaping the passband so that the center frequency is placed near a target of the target center frequency.
 11. The RF front-end circuitry of claim 1 wherein the calibration circuit comprises a replica resonator and the calibration circuit is configured to shape the passband so that the passband defines the center frequency near the target center frequency using the replica resonator.
 12. The RF front-end circuitry of claim 11 wherein the calibration circuit is configured to adjust the phase difference of the pair of weakly coupled resonators after shaping the passband so that the center frequency is placed near a target of the target center frequency using the replica resonator.
 13. The RF front-end circuitry of claim 1 wherein the calibration circuit is configured to adjust the phase difference of the pair of weakly coupled resonators at the target center frequency so as to eliminate the frequency displacement between the center frequency of the passband and the target center frequency.
 14. The RF front-end circuitry of claim 1 wherein the calibration circuit is configured to adjust the phase difference of the pair of weakly coupled resonators at the target center frequency so as to reduce the frequency displacement between the center frequency of the passband and the target center frequency by being configured to adjust the phase difference at the target center frequency so as to reduce a phase displacement between the phase difference at the target center frequency and a first target phase difference at the target center frequency.
 15. The RF front-end circuitry of claim 14 wherein the first target phase difference at the target center frequency has a magnitude of 90 degrees.
 16. The RF front-end circuitry of claim 1 wherein the pair of weakly coupled resonators comprises a first resonator and a second resonator weakly coupled to the first resonator and wherein the tunable RF filter structure comprises: a first terminal; a second terminal; a first tunable RF filter path that is connected between the first terminal and the second terminal and that defines the passband of the transfer function, wherein the first tunable RF filter path includes the first resonator and the second resonator and; a third resonator weakly coupled to the first resonator and the second resonator.
 17. The RF front-end circuitry of claim 16 wherein: the first tunable RF filter path further includes a first cross-coupling capacitive structure having a variable capacitance, wherein the first cross-coupling capacitive structure is connected between the first resonator and the second resonator; and the calibration circuit is configured to adjust the phase difference of the pair of weakly coupled resonators at the target center frequency so as to reduce the frequency displacement between the center frequency of the passband and the target center frequency by being configured to adjust the variable capacitance of the first cross-coupling capacitive structure.
 18. The RF front-end circuitry of claim 16 wherein the calibration circuit is further configured to: detect a second phase difference at the target center frequency between the first resonator and the third resonator; and detect a third phase difference at the target center frequency between the third resonator and the second resonator; adjust the second phase difference at the target center frequency between the first resonator and the third resonator and the third phase difference at the target center frequency between the third resonator and the second resonator so that the second phase difference at the target center frequency in combination with the third phase difference at the target center frequency is constructive with phase difference at the target center frequency between the pair of weakly coupled resonators.
 19. The RF front-end circuitry of claim 18 wherein: the first tunable RF filter path further includes a first cross-coupling capacitive structure having a variable capacitance, wherein the first cross-coupling capacitive structure is connected between the first resonator and the second resonator; the tunable RF filter structure further comprises: a second cross-coupling capacitive structure having a variable capacitance wherein the second cross-coupling capacitive structure is connected between the first resonator and the third resonator; a third cross-coupling capacitive structure having a variable capacitance wherein the third cross-coupling capacitive structure is connected between the third resonator and the first resonator.
 20. The RF front-end circuitry of claim 19 wherein the calibration circuit is configured to adjust the phase difference of the pair of weakly coupled resonators at the target center frequency so as to reduce the frequency displacement between the center frequency of the passband and the target center frequency by being configured to adjust the variable capacitance of the first cross-coupling capacitive structure and wherein the calibration circuit is further configured to adjust the second phase difference at the target center frequency between the first resonator and the third resonator and the third phase difference at the target center frequency between the third resonator and the second resonator so that the second phase difference at the target center frequency in combination with the third phase difference at the target center frequency is constructive with the phase difference at the target center frequency between the pair of weakly coupled resonators by being configured to adjust the variable capacitance of the second cross-coupling capacitive structure and the variable capacitance of the third cross-coupling capacitive structure.
 21. The RF front-end circuitry of claim 18 wherein the calibration circuit is further configured to: detect the phase difference at a target notch frequency between the pair of weakly coupled resonators; detect the second phase difference at the target notch frequency between the first resonator and the third resonator; detect the third phase difference at the target notch frequency between the third resonator and the second resonator; and create a notch approximately at the target notch frequency by being configured to adjust the phase difference at the target notch frequency between the pair of weakly coupled resonators, the second phase difference at the target notch frequency between the first resonator and the third resonator and the third phase difference at the target notch frequency between the third resonator and the second resonator so that the second phase difference at the target notch frequency in combination with the third phase difference at the target notch frequency is destructive with the phase difference at the target notch frequency between the pair of weakly coupled resonators.
 22. The RF front-end circuitry of claim 18 wherein the calibration circuit is further configured to detect phase differences measured at frequencies different than a target notch frequency and have relations such that the phase differences are adjusted to create a notch at the target notch frequency.
 23. The RF front-end circuitry of claim 16 wherein the tunable RF filter structure further comprises a coupling capacitive structure connected between the first terminal and the first resonator.
 24. The RF front-end circuitry of claim 23 wherein the calibration circuit is further configured to: detect a second phase difference at the target center frequency between the coupling capacitive structure and the first resonator; detect a third phase difference at the target center frequency between the first resonator and the third resonator; and adjust the second phase difference at the target center frequency between the coupling capacitive structure and the first resonator and the third phase difference at the target center frequency between the first resonator and the third resonator so that the second phase difference at the target center frequency is constructive with the third phase difference at the target center frequency between the first resonator and the third resonator.
 25. The RF front-end circuitry of claim 23 wherein the calibration circuit is further configured to: detect a second phase difference at a target notch frequency between the coupling capacitive structure and the first resonator; detect a third phase difference at the target notch frequency between the first resonator and the third resonator; and create a notch approximately at the target notch frequency by being configured to adjust the second phase difference at the target notch frequency between the coupling capacitive structure and the first resonator and the third phase difference at the target notch frequency between the first resonator and the third resonator so that the second phase difference at the target notch frequency is destructive with the third phase difference at the target notch frequency between the first resonator and the third resonator.
 26. The RF front-end circuitry of claim 1 wherein the calibration circuit comprises: one or more phase detectors; a calibration computational device operably associated with the one or more phase detectors; and a tuning control device operably associated with the tunable RF filter structure.
 27. A calibration method for a tunable radio frequency (RF) filter structure, comprising: shape a passband so that the passband defines a target center frequency, wherein the tunable RF filter structure has a transfer function that defines the passband; detect a phase difference at the target center frequency between a pair of weakly coupled resonators in the tunable RF filter structure; and adjust the phase difference of the pair of weakly coupled resonators at the target center frequency so as to reduce a frequency displacement between a center frequency of the passband and the target center frequency. 